99942 Apophis#Planetary Society competition

File:Apophis model comparison.png

File:Size of Apophis asteroid.png and Empire State Building]]

Based on the observed brightness, Apophis's diameter was initially estimated at {{convert|450|m}}; a more refined estimate based on spectroscopic observations at NASA's Infrared Telescope Facility in Hawaii by Binzel, Rivkin, Bus, and Tokunaga (2005) is {{convert|350|m}}. As of 2013, NASA's impact risk page listed the diameter at {{convert|330|m}}, and an assumed mass of 4{{X10^|10}} kg. The mass estimate is more approximate than the diameter estimate, but should be accurate to within a factor of three. Apophis's surface composition probably matches that of LL chondrites.

Based on Goldstone and Arecibo radar images taken in 2012–2013, Brozović et al. have estimated that Apophis is an elongated object 450 × 170 metres in size, and that it is bilobed (possibly a contact binary) with a relatively bright surface albedo of {{val|0.35|0.10}}. The axis of its angular momentum points 59° south of the ecliptic, which means that Apophis is a retrograde rotator. Apophis is a tumbler, which means that it does not rotate around a fixed axis. Rather, the axis of rotation moves in the frame of reference of the asteroid with a period of around 263 hours (called the rotation period). The angle between it and the principal axis of highest moment of inertia varies, as does the angle between that principal axis and the vector of angular momentum (from around 12° to around 55° twice every period). During this period, the angle between the long axis of Apophis and the angular momentum vector swings between around 78° and 102° (90°±12°). But the principal axis of highest moment and the rotation axis both move around the constant axis of angular momentum much faster, with a time-averaged period of 27.38 hours (this is called precession). The result is that Apophis appears to be flipping, making a revolution on average every 30.56 hours. Every 263 hours, the principal axis with highest moment goes around 263/27.28 times (ca 9.6), whereas the long axis goes around 263/30.56 times (ca 8.6).

File:Change in orbit of Apophis in 2029.png. This gives the distance from Earth's orbit at the points where the solid curves cross the yellow curve.]]

Apophis has a low inclination orbit (3.3°) that varies from just outside the orbit of Venus (0.746 AU, as compared to the aphelion of Venus, 0.728) to just outside the orbit of Earth (1.099 AU). Although its orbit changes slightly each time it comes close to Earth, at present it comes near Earth once in 7.75 years on average (four times between April 14, 1998, and April 13, 2029). Because of its eccentric orbit, these moments are not evenly spaced and tend to occur between December and April, when Apophis is in the outer portions of its orbit. In fact, the eccentricity and semi-major axis are such that (before 2029) Apophis is always receding from Earth around May 1 and is always approaching around December 2.See "deldot" in [https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=apophis&START_TIME=%271900-5-1%27&STOP_TIME=%272029-4-25%27&STEP_SIZE=%271%20years%27&QUANTITIES=%2718%2019%2020%2031 this JPL Horizons simulation] and [https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=apophis&START_TIME=%271900-12-2%27&STOP_TIME=%272029-4-25%27&STEP_SIZE=%271%20years%27&QUANTITIES=%2718%2019%2020%2031 this one]. At the ascending node (where Apophis crosses the plane of Earth's orbit from south to north) Apophis is very close to where Earth is around April 13 of any year, and this is what gives rise to close encounters such as the one on April 13, 2029. The orbit also passes south of where the earth is in mid December, producing for example the close approaches of December 16, 1889, and December 18, 1939. After the 2029 Earth approach, the orbit will change dramatically. The period will change from around {{Fraction|8|9}} of a year to a bit under {{Fraction|7|6}}. It will still come very close to Earth's yearly April 13 location. It will no longer pass close to Earth's yearly mid-December location, but will then pass close to Earth's mid-September location. This will cause a close encounter on September 11, 2102, after which the uncertainty in the location of Apophis will increase rapidly with time.

The closest known approach of Apophis will occur on April 13, 2029, at 21:46 UT, when Apophis will pass Earth at a distance of about {{convert|31600|km|lk=on}} above the surface.2029-Apr-13 approach: {{Convert|0.000254093|AU|km|abbr=on|lk=on}}. [https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=Apophis&view=OPC 38012km "geocentric distance"] – 6378km "Earth radius" = 31634km{{Cite web |last=Shekhtman |first=Lonnie |date=September 24, 2023 |title=OSIRIS-REx Spacecraft Departs for New Mission |url=https://blogs.nasa.gov/osiris-rex/2023/09/24/osiris-rex-spacecraft-departs-for-new-mission/ |access-date=2025-04-14 |website=NASA}} Using the June 2024 orbit solution which includes the Yarkovsky effect, the 3-sigma uncertainty region in the 2029 approach distance is about ±3.3 km. The distance, a hair's breadth in astronomical terms, is five times the radius of the Earth, one tenth the distance to the Moon,{{Cite web|url=https://blogs.nasa.gov/osiris-rex/2023/09/24/osiris-rex-spacecraft-departs-for-new-mission/|title=OSIRIS-REx Spacecraft Departs for New Mission|date=September 24, 2023}} and closer than the ring of geostationary satellites currently orbiting the Earth.{{Cite web|url=https://www.satsig.net/sslist.htm|title=List of satellites in geostationary orbit|website=satsig.net}} It will be the closest asteroid of its size in recorded history. On that date, it will become as bright as magnitude 3.1 (visible to the naked eye from rural as well as darker suburban areas, visible with binoculars from most locations). The close approach will be visible from Europe, Africa, and western Asia. Over the course of about a day, Apophis will move northwest from Centaurus to Perseus and then southwest to Pisces, an arc of 205°.From ecliptic longitude and latitude of 221°, −16° to 16°, 12° (according to [https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=apophis&START_TIME=%272029-4-1%27&STOP_TIME=%272029-4-25%27&STEP_SIZE=%271%20days%27&QUANTITIES=%2718%2019%2020%2031 this Horizons run]), or in right ascension and declination, from 14h14m, −30°17' to 0h39m, 16°51' (using [https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=apophis&START_TIME=%272029-4-1%27&STOP_TIME=%272029-4-25%27&STEP_SIZE=%271%20days%27&QUANTITIES='2 29' this] and [https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=apophis&START_TIME=%272029-4-13%27&STOP_TIME=%272029-4-15%27&STEP_SIZE=%271%20hour%27&QUANTITIES=%272%2029%27 this]). Approaching Earth its speed relative to Earth will be 6.0 km/s. Earth's gravity will accelerate it to 7.4 km/s at the time of closest approach, and then slow it back down to 6 as it departs.According to [https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=apophis&START_TIME=%272029-4-1%2021:46%27&STOP_TIME=%272029-4-25%27&STEP_SIZE=%271%20days%27&QUANTITIES=22 this JPL Horizons run]. During the approach, Earth will perturb Apophis from an Aten-class orbit with a semi-major axis of 0.92 AU to an Apollo-class orbit with a semi-major axis of 1.1 AU. Perihelion will lift from 0.746 AU to 0.895 AU and aphelion will lift from 1.10 AU to 1.31 AU.

During the 2029 approach, Apophis's brightness will peak at magnitude 3.1, easily visible to the naked eye, with a maximum angular speed of 42° per hour. The maximum apparent angular diameter will be approximately 2 arcseconds. This is roughly equivalent to the angular diameter of Neptune from earth. Therefore, the asteroid will be barely resolved by ground-based telescopes not equipped with adaptive optics but very well resolved by those that are. Because the approach will be so close, tidal forces are likely to alter Apophis's rotation axis, but Apophis will not approach within the Roche limit where it would be broken up by tidal forces. A partial resurfacing of the asteroid is possible, which might change its spectral class from a weathered Sq- to an unweathered Q-type.

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| image1 = Animation of 99942 Apophis orbit around Sun.gif

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| footer ={{Legend inline| yellow| Sun}}{{·}}{{Legend inline| RoyalBlue| Earth}}{{·}}{{Legend inline| Magenta| 99942 Apophis }}{{·}}{{Legend inline| Gold| Moon}}

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{{Large near earth asteroid flybys 2LD}}

In 2036, Apophis will pass the Earth at a third the distance of the Sun in both March and December. Using the 2024 orbit solution, the Earth approach on March 27, 2036, will be no closer than {{convert|0.3089|AU|e6km e6mi LD|abbr=unit|lk=in}}, but more likely about {{convert|0.3097|AU|e6km e6mi|abbr=unit}}. For comparison, the planet Venus will be closer to Earth at {{convert|0.2883|AU|e6km e6mi LD|abbr=unit|lk=off}} on May 30, 2036.{{Cite web|url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27299%27&START_TIME=%272036-05-30%2002:10%27&STOP_TIME=%272036-05-30%2002:30%27&STEP_SIZE=%271%20min%27&QUANTITIES=%2720%27|title=Venus 2036-May-30 @ JPL Horizons}}{{efn|name=Venus2022}} On December 31, 2036, Apophis will be a little bit further away than the March approach at about {{convert|0.33|AU|e6km e6mi|abbr=unit}}.

Around April 19–20, 2051, Apophis will pass about {{convert|0.04|AU|e6km e6mi|abbr=unit|lk=off}} from Earth and it will be the first time since 2029 that Apophis will pass within 10 million km of Earth.

Although early simulations showed that there was a chance Apophis could hit the earth on April 12, 2068, this was later excluded and JPL Horizons calculates that Apophis will be about {{convert|1.864|+/-|0.0024|AU|e6km|abbr=unit|lk=off}} from Earth, making the asteroid much farther than the Sun.

By 2116, the JPL Small-Body Database and NEODyS close approach data start to become divergent. In April 2116, Apophis is expected to pass about {{convert|0.02|AU|e6km LD|abbr=unit|sigfig=1}} from Earth, but could pass as close as {{convert|0.001|AU|e3km LD|abbr=unit}} or as far as {{convert|0.1|AU|e6km LD|abbr=unit}}.

Six months after discovery, and shortly after a close approach to Earth on December 21, 2004, the improved orbital estimates led to the prediction of a very close approach on April 13, 2029, by both NASA's automatic Sentry system and NEODyS, a similar automatic program run by the University of Pisa and the University of Valladolid. Subsequent observations decreased the uncertainty in Apophis's trajectory and the probability of an impact event in 2029 temporarily climbed, peaking at 2.7% (1 in 37) on December 27, 2004, when the uncertainty region had shrunk to 83,000 km. This probability, combined with its size, caused Apophis to be assessed at level 4 on the Torino scale and 1.10 on the Palermo scale (corresponding to an impact hazard over 12 times the background level), scales scientists use to represent how dangerous a given asteroid is to Earth. These are the highest values at which any object has been rated on either scale. The chance that there would be an impact in 2029 was eliminated later in the day of December 27, 2004, as a result of a precovery image that extended the observation arc back to March 2004. The danger of a 2036 passage was lowered to level 0 on the Torino scale in August 2006. With a cumulative Palermo scale rating of −3.22, the risk of impact from Apophis is less than one thousandth the background hazard level.

In July 2005, former Apollo astronaut Rusty Schweickart, as chairman of the B612 Foundation, formally asked NASA to investigate the possibility that the asteroid's post-2029 orbit could be in orbital resonance with Earth, which would increase the probability of future impacts. Schweickart also asked NASA to investigate whether a transponder should be placed on the asteroid to enable more accurate tracking of how its orbit is affected by the Yarkovsky effect.

On January 31, 2011, astronomers took the first new images of Apophis in more than three years.

File:Apophis ellipse.svg

The close approach in 2029 will substantially alter the object's orbit, prompting Jon Giorgini of JPL to say in 2011, "If we get radar ranging in 2013 [the next good opportunity], we should be able to predict the location of {{Minor planet|2004 MN|4}} out to at least 2070." Apophis passed within {{convert|0.0966|AU|e6km e6mi|abbr=unit|lk=off}} of Earth in 2013, allowing astronomers to refine the trajectory for future close passes. Just after the closest approach on January 9, 2013, the asteroid peaked at an apparent magnitude of about 15.6. The Goldstone radar observed Apophis during that approach from January 3 through January 17. The Arecibo Observatory observed Apophis once it entered Arecibo's field of view after February 13, 2013. The 2013 observations basically ruled out any chance of a 2036 impact.

A NASA assessment as of February 21, 2013, that did not use the January and February 2013 radar measurements gave an impact probability of 2.3 in a million for 2068. As of May 6, 2013, using observations through April 15, 2013, the odds of an impact on April 12, 2068, as calculated by the JPL Sentry risk table had increased slightly to 3.9 in a million (1 in 256,000).

Incorporating early 2015 observations, the April 12, 2068, impact probability was 6.7 in a million (1 in 150,000), and the asteroid had a cumulative 9 in a million (1 in 110,000) chance of impacting Earth before 2106. After 2015, its orbit kept it near the Sun from the perspective of Earth, precluding telescopic observations. It was not further than 60 degrees from the Sun between April 2014 and December 2019.

File:Apophis February 2021 NBO.webm

No observations of Apophis were made between January 2015 and February 2019 but observations began again in January 2020. In March 2020, astronomers David Tholen and Davide Farnocchia measured the acceleration of Apophis due to the Yarkovsky effect for the first time, significantly improving the prediction of its orbit past the 2029 flyby. Tholen and Farnocchia found that the Yarkovsky effect causes the semi-major axis to decrease by about 170 metres per year, causing an increase in ecliptic longitude that is quadratic in time. In late 2020 Apophis approached the Earth and passed {{convert|0.11265|AU|e6km LD|abbr=unit}} from Earth on March 6, 2021, brightening to +15 mag at that time. Radar observations of Apophis were carried out at Goldstone in March 2021. The asteroid has been observed by NEOWISE (between December 2020 and April 2021) and by NEOSSat (in January 2021).

These observations showed that the impact parameter ζ (basically how far behind Earth Apophis would pass if it were not deflected by the gravitational pull of Earth) in 2029 will be about 47,363 km,{{cite journal |last1=Jorge A. Pérez-Hernández & Luis Benet |title=Non-zero Yarkovsky acceleration for near-Earth asteroid (99942) Apophis |journal=Nature Communications Earth & Environment |date=January 11, 2022 |volume=3 |issue=1 |page=10 |doi=10.1038/s43247-021-00337-x |doi-access=free |bibcode=2022ComEE...3...10P }} less than the earlier nominal value of 47,659 km by 296 km because of the Yarkovsky effect. This means that Apophis will not hit Earth in the coming century, in particular avoiding the keyhole 212.14 km below nominal that would have led to a collision in 2068.

Apophis was the target of an observing campaign by the International Asteroid Warning Network, resulting in the collection of light curves, spectra, and astrometry. The observations were used to practice and coordinate the response to an actual impact threat. Ignoring all earlier observations, the estimated probability of an impact in 2029 reached 16 percent before going down to zero.

File:Apophis impact risk corridor 2029.jpg

On February 21, 2021, Apophis was removed from the Sentry Risk Table, as an impact in the next 100 years was finally ruled out.[https://cneos.jpl.nasa.gov/sentry/removed.html Removed Objects] from Sentry Risk Table

Several occultations of bright stars (apparent magnitude 8–11) by Apophis occurred in March and April 2021. A total of five separate occultations were observed successfully, marking the first time that an asteroid as small as Apophis was observed using the occultation method (beating the previous record set in 2019 by asteroid 3200 Phaethon, which is more than ten times the size of Apophis). The first event, on March 7, was successfully observed from the United States by multiple observers. The next potential occultation, which occurred on March 11, was predicted to be visible from central Europe, but was not observed, mainly because of bad weather (two negative observations were recorded from Greece). Another occultation occurred on March 22, but larger-than-expected residuals in the March 7 data had caused the majority of observers to be deployed outside of the actual path for the occultation, and it was observed only by a single observer from the United States, amateur astronomer Roger Venable. This single detection then allowed the prediction of several more events that would have been unobservable otherwise, including an occultation on April 4, which was observed from New Mexico, again by Venable, alongside others. Two more occultations, observable on April 10 and 11 from Japan and New Mexico, respectively, were seen by several observers each. The occultation measurements allowed refinement of the measurement of the asteroid size and orbit.

On March 9, 2021, using radar observations from Goldstone taken on March 3–8 and three positive detections of the stellar occultation on March 7, 2021, Apophis became the asteroid with the most precisely measured Yarkovsky effect of all asteroids, at a signal-to-noise ratio (SNR) of 186.4,{{efn|name=Yarkovsky_20210309}} surpassing 101955 Bennu (SNR=181.6).

The 2021 apparition was the last opportunity to observe Apophis before its 2029 flyby.

File:PIA24168-Asteroid-99942Apophis-RadarImages-20210326.jpg

As of 2021, the Sentry Risk Table estimated that Apophis would impact Earth with kinetic energy equivalent to 1,200 MT or megatons of TNT. In comparison, the energy released by the eruption of Krakatoa was 200 MT, the total global nuclear arsenal has an energy equivalent to 1,460 MT, and the Chicxulub impact and extinction event had an estimated energy of 100,000,000 MT (100 teratons). See TNT equivalent examples for an extended table of comparable energies.

The exact effects of an impact would vary based on the asteroid's composition, and the location and angle of impact. Any impact of Apophis would be extremely detrimental to an area of thousands of square kilometres, but would be unlikely to have long-lasting global effects, such as the initiation of an impact winter.{{Cite journal|last1=Baurov|first1=Y.A.|last2=Albanese|first2=L.|last3=Meneguzzo|first3=F.|last4=Menshikov|first4=V.A.|title=Protecting the planet from the asteroid hazard|url=https://www.researchgate.net/publication/260818491|year=2013|volume=9|issue=3|journal=Int. J. Pure Appl. Phys. |pages=151–168}} Assuming Apophis is a {{convert|370|m|ft|adj=mid|-wide}} stony asteroid with a density of 3,000 kg/m³, if it were to impact into sedimentary rock, Apophis would create a {{convert|5.1|km|ft|adj=mid}} impact crater.

In 2008, the B612 Foundation made estimates of Apophis's path if a 2036 Earth impact were to occur, as part of an effort to develop viable deflection strategies. The result was a narrow corridor a few kilometres wide, called the "path of risk", extending across southern Russia, across the north Pacific (relatively close to the coastlines of California and Mexico), then right between Nicaragua and Costa Rica, crossing northern Colombia and Venezuela, ending in the Atlantic, just before reaching Africa.Range of Possible Impact Points on April 13, 2036 in [http://www.aero.org/conferences/planetarydefense/2007papers/S3-4--Gennery-Brief.pdf Scenarios for Dealing with Apophis], by Donald B. Gennery, presented at the Planetary Defense Conference. Washington, DC. March 5–8, 2007 (archived from [https://web.archive.org/web/20120412123940/http://www.aero.org/conferences/planetarydefense/2007papers/S3-4--Gennery-Brief.pdf the original] on April 12, 2012). Using the computer simulation tool NEOSim, it was estimated that the hypothetical impact of Apophis in countries such as Colombia and Venezuela, which were in the path of risk, could have more than 10 million casualties. A deep-water impact in the Atlantic or Pacific oceans would produce an incoherent short-range tsunami with a potential destructive radius (inundation height of >2 m) of roughly {{convert|1000|km}} for most of North America, Brazil and Africa, {{convert|3000|km|abbr=on}} for Japan and {{convert|4500|km|abbr=on}} for some areas in Hawaii.

The OSIRIS-REx spacecraft returned a sample of Bennu to Earth on September 24, 2023.{{cite report|title=OSIRIS-REx factsheet|date=August 2011|publisher=NASA|department=Explorers and Heliophysics Projects Division|place=Goddard SFC|website=ehpd.gsfc.nasa.gov|url=https://ehpd.gsfc.nasa.gov/documents/552572main_OSIRIS_REx_Factsheet.pdf}} {{Source-attribution}} After ejecting the sample canister, the spacecraft can use its remaining fuel to target another body during an extended mission. Apophis is the only asteroid which the spacecraft could reach for a long-duration rendezvous, rather than a brief flyby. In April 2022, the extension was approved, and OSIRIS-REx will perform a rendezvous with Apophis in April 2029, a few days after the close approach to Earth. It will study the asteroid for 18 months and perform a maneuver similar to the one it made during sample collection at Bennu, by approaching the surface and firing its thrusters. This will expose the asteroid's subsurface and allow mission scientists to learn more about the asteroid's material properties. For its Apophis mission after the sample return, OSIRIS-REx was renamed OSIRIS-APEX (short for OSIRIS-Apophis Explorer).{{Cite web|date=April 25, 2022|title=NASA gives green light for OSIRIS-REx spacecraft to visit another asteroid|url=https://news.arizona.edu/story/nasa-gives-green-light-osiris-rex-spacecraft-visit-another-asteroid|access-date=April 26, 2022|publisher=University of Arizona News|first=Mikayla|last=Mace Kelley}}

In 2007, the Planetary Society, a California-based space advocacy group, organised a $50,000 competition to design an uncrewed space probe that would 'shadow' Apophis for almost a year, taking measurements that would "determine whether it will impact Earth, thus helping governments decide whether to mount a deflection mission to alter its orbit". The society received 37 entries from 20 countries on 6 continents.{{Cite web|url=https://www.planetary.org/press-releases/0226_planetary_society_names_winners_of|title=Planetary Society Names Winners of $50,000 Asteroid Tagging Competition|last=Kaplan|first=Mat|date=February 26, 2008|website=www.planetary.org|archive-url=https://web.archive.org/web/20200812145258/https://www.planetary.org/press-releases/0226_planetary_society_names_winners_of|archive-date=August 12, 2020|url-status=live}}

The commercial competition was won by a design called Foresight created by SpaceWorks Engineering.{{clarify|date=November 2024|reason=An earlier version of this article stated that the competition was won by SpaceWorks Enterprises, but both sources disagree. Is this a different name for the same company?}} SpaceWorks proposed a simple orbiter with only two instruments and a radio beacon at a cost of ~US$140 million, launched aboard a Minotaur IV between 2012 and 2014. Pharos, the winning student entry, would be an orbiter with four science instruments that would rendezvous with and track Apophis. The spacecraft would have been launched in April or May 2013 aboard a Delta II 7925 rocket, to arrive at the asteroid after a cruise of 233 to 309 days. It would have carried four additional BUOI probes that would have impacted the surface of Apophis over the course of two weeks.{{Cite web|url=https://ntrs.nasa.gov/api/citations/20120000562/downloads/20120000562.pdf|title=PHAROS: Shedding Light on the Near-Earth Asteroid Apophis|work=ESMD Space Grant Systems Engineering Paper Competition|date=April 30, 2007|publisher=Georgia Institute of Technology|first1=Jonathan|last1=Sharma|first2=Jarret|last2=Lafleur|first3=Nilesh|last3=Shah|first4=Jilian|last4=Apa|first5=Jonathan|last5=Townley|first6=Kreston|last6=Barron|archive-url=https://web.archive.org/web/20241115143132/https://ntrs.nasa.gov/api/citations/20120000562/downloads/20120000562.pdf|archive-date=November 15, 2024|url-status=live}}

Apophis is one of two asteroids that were considered by the European Space Agency as the target of its Don Quijote mission concept to study the effects of impacting an asteroid.

China had planned an encounter with Apophis in 2022, several years prior to the close approach in 2029. This mission, now known as Tianwen-2, would have included exploration and close study of three asteroids including an extended encounter with Apophis for close observation, and land on the asteroid 1996 FG₃ to conduct in situ sampling analysis on the surface. The launch date is now scheduled for May 2025, with a different set of targets.{{cite web|last=Jones|first=Andrew|url=https://spacenews.com/china-conducts-parachute-tests-for-asteroid-sample-return-mission/|title=China conducts parachute tests for asteroid sample return mission|work=SpaceNews|date=June 26, 2023|access-date=October 28, 2024}}

Apophis is the target of the European Space Agency's proposed RAMSES (Rapid Apophis Mission for Security and Safety) mission, with a launch in 2026–2028{{efn|1=Mannocchi et al. give possible launch dates of November–December 2026, April–May 2027, September–November 2027, or March–May 2028, with a launch in 2027 being the preferred option.}} and rendezvous with the asteroid in 2029.{{cite arXiv|last1=Morelli|first1=Andrea C.|last2=Mannocchi|first2=Alessandra|display-authors=etal|date=September 2023|title=Initial Trajectory Assessment of the RAMSES Mission to (99942) Apophis|eprint=2309.00435|class=astro-ph.EP}}{{cite web|last1=Bartels|first1=Meghan|title=Europe Announces New Mission to Infamous Asteroid Apophis|url=https://www.scientificamerican.com/article/asteroid-apophis-is-target-of-europes-new-ramses-mission/|work=Scientific American|access-date=October 28, 2024}}

{{further|Asteroid impact avoidance}}

Studies by NASA, ESA, and various research groups in addition to the Planetary Society contest teams, have described a number of proposals for deflecting Apophis or similar objects, including gravitational tractor, kinetic impact, and nuclear bomb methods.

On December 30, 2009, Anatoly Perminov, the director of the Russian Federal Space Agency, said in an interview that Roscosmos will also study designs for a possible deflection mission to Apophis.

On August 16, 2011, researchers at China's Tsinghua University proposed launching a mission to knock Apophis onto a safer course using an impactor spacecraft in a retrograde orbit, steered and powered by a solar sail. Instead of moving the asteroid on its potential resonant return to Earth, Shengping Gong and his team believe the secret is shifting the asteroid away from entering the gravitational keyhole in the first place.

On February 15, 2016, Sabit Saitgarayev, of the Makeyev Rocket Design Bureau, announced intentions to use Russian ICBMs to target relatively small near-Earth objects. Although the report stated that likely targets would be between the 20 to 50 metres in size, it was also stated that 99942 Apophis would be an object subject to tests by the program.

In October 2022, a method of mapping the inside of a potentially problematic asteroid, such as 99942 Apophis, in order to determine the best area for impact was proposed.{{cite news|last=Verma|first=Pranshu|title=There's a new tool to help blow up asteroids – Researchers from MIT and Stanford have created a tool that could improve the aim of future planetary defense missions|url=https://www.washingtonpost.com/technology/2022/10/21/asteroid-destruction-tool/|date=October 21, 2022|newspaper=The Washington Post|access-date=October 22, 2022}}

In Id Software's video game Rage, the backstory involves the asteroid colliding with Earth on August 23, 2029. The asteroid almost wipes out the human race and ushers in a post-apocalyptic age.

In music, the asteroid Apophis was referenced in the song "The Profit of Doom" by gothic metal band Type O Negative on their 2007 album Dead Again. The lyrics refer to the asteroid 99942 Apophis, which at that time was considered to have a possibility of hitting Earth on Friday, April 13, 2029.

{{div col|colwidth=20em}}

• Asteroid capture
• Asteroid impact prediction
• Asteroid Redirect Mission
• Earth-grazing fireball
• List of impact structures on Earth
• NEO Surveyor
• List of predicted asteroid impacts on Earth

{{div col end}}

{{notelist|refs=

{{efn|name=palermo|Of the six asteroids with a higher Palermo scale rating than Apophis at the time:

• (29075) 1950 DA and 101955 Bennu cannot impact within the next 100 years;
• 1979 XB and 2007 FT3 are lost short-arc objects that cannot be recovered with targeted observations and await serendipitous survey observations;
• 2000 SG344 and 2009 JF1 are less than 50 metres in diameter.}}

{{efn|name=Yarkovsky_20210309|Using the March 9, 2021, solution, JPL gave the strength of the Yarkovsky effect as $A\_\{2\}=-2.877\backslash times10^\{-14\}\backslash text\{\; AU/d\}^\{2\}$, with an uncertainty of $1.543\backslash times10^\{-16\}\backslash text\{\; AU/d\}^\{2\}$. The SNR, defined as the size of the signal divided by the uncertainty, is $2.877\backslash times10^\{-14\}/1.543\backslash times10^\{-16\}=186.4$. As of the latest orbit solution (June 29, 2021), the SNR is $2.901\backslash times10^\{-14\}/1.942\backslash times10^\{-16\}=149.4$ (again lower than Bennu's).}}

{{efn|name=Venus2022|On January 8, 2022 Venus was even closer to Earth at {{convert|0.2658|AU|e6km e6mi LD|abbr=unit|lk=off}}.}}

}}

{{reflist|refs =

{{cite web|type=last observation: April 09, 2022; arc: 18.07 years; JPL #220 solution date: 2024-Jun-25|title=JPL Small-Body Database Browser: 99942 Apophis (2004 MN4)|url=https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=Apophis&view=OPC|access-date=February 28, 2025}}

{{cite web|title=NEODyS : (99942) Apophis (Close Approaches)|publisher=NEODyS (Near Earth Objects—Dynamic Site)|url=https://newton.spacedys.com/neodys/index.php?pc=1.1.8&n=99942|access-date=March 14, 2021}}

{{cite web|title=(99942) Apophis Orbit|publisher=IAU Minor Planet Center|url=http://www.minorplanetcenter.net/db_search/show_object?object_id=99942|access-date=April 1, 2021}}

{{cite web|url=http://www.esa.int/Our_Activities/Space_Science/Herschel_intercepts_asteroid_Apophis|title=Herschel intercepts asteroid Apophis|author=ESA|publisher=European Space Agency (ESA)|date=January 9, 2013|access-date=January 9, 2013}}

{{cite web|title=99942 Apophis 2013 Goldstone Radar Observations Planning|publisher=NASA/JPL Asteroid Radar Research|last=Benner|first=L. A. M.|url=http://echo.jpl.nasa.gov/asteroids/Apophis/Apophis_2013_planning.html|date=January 9, 2013|access-date=January 9, 2013}}

{{cite web|date=January 9, 2013|title=Asteroid Apophis Takes a Pass in 2036|publisher=Sky & Telescope|author=Kelly Beatty|url=http://www.skyandtelescope.com/astronomy-news/asteroid-apophis-takes-a-pass-in-2036/|access-date=November 10, 2014}}

{{cite journal|url=https://echo.jpl.nasa.gov/asteroids/brozovic.etal.apophis.2018.pdf|title=Goldstone and Arecibo radar observations of (99942) Apophis in 2012–2013|first1=M.|last1=Brozović|first2=L. A. M.|last2=Benner|first3=J. G.|last3=McMichael|first4=J. D.|last4=Giorgini|first5=P.|last5=Pravec|first6=P.|last6=Scheirich|first7=C.|last7=Magric|first8=M. W.|last8=Busch|first9=J. S.|last9=Jao |first10=C. G. |last10=Lee|first11=L. G.|last11=Snedeker|first12=M. A.|last12=Silva|first13=M. A.|last13=Slade|first14=B.|last14=Semenov|first15=M. C.|last15=Nolan|first16=P. A.|last16=Taylor|first17=E. S.|last17=Howell|first18=K. J.|last18=Lawrence|display-authors=4|journal=Icarus|volume=300|date=January 15, 2018|pages=115–128|access-date=August 19, 2018|bibcode=2018Icar..300..115B|doi=10.1016/j.icarus.2017.08.032}}

{{cite web|title=NASA Rules Out Earth Impact in 2036 for Asteroid Apophis|publisher=NASA|url=http://www.jpl.nasa.gov/news/news.php?release=2013-017|date=January 10, 2013|access-date=January 10, 2013}}

{{cite journal|title=Impact Threat from Near-Earth Asteroid Apophis in 2036 Now Ruled Out|publisher=Bad Astronomy blog|author=Phil Plait|journal=Slate|author-link=Phil Plait|url=http://www.slate.com/blogs/bad_astronomy/2013/01/10/apophis_impact_new_observation_show_it_to_be_bigger_but_no_longer_a_threat.html|date=January 10, 2013|access-date=January 10, 2013}}

{{cite web|title=99942 Apophis|publisher=The Near-Earth Asteroids Data Base at E.A.R.N|url=http://earn.dlr.de/nea/099942.htm|access-date=October 15, 2009|archive-url=https://web.archive.org/web/20120616092526/http://earn.dlr.de/nea/099942.htm|archive-date=June 16, 2012|url-status=dead}}

{{cite journal|title=The tumbling spin state of (99942) Apophis|last1=Pravec|first1=P.|last2=Scheirich|first2=P.|last3=Ďurech|first3=J.|last4=Pollock|first4=J.|last5=Kušnirák|first5=P.|last6=Hornoch|first6=K.|last7=Galád|first7=A.|last8=Vokrouhlický|first8=D.|last9=Harris|first9=A.W. |last10=Jehin |first10=E.|last11=Manfroid|first11=J.|last12=Opitom|first12=C.|last13=Gillon|first13=M.|last14=Colas|first14=F.|last15=Oey|first15=J.|last16=Vraštil|first16=J.|last17=Reichart|first17=D.|last18=Ivarsen|first18=K.|last19=Haislip|first19=J. |last20=LaCluyze |first20=A.|display-authors=4|journal=Icarus|date=2014|url=http://sajri.astronomy.cz/pravecetal2014.pdf|volume=233|pages=48–60|doi=10.1016/j.icarus.2014.01.026|bibcode=2014Icar..233...48P|access-date=November 26, 2014|archive-date=March 5, 2016|archive-url=https://web.archive.org/web/20160305030401/http://sajri.astronomy.cz/pravecetal2014.pdf|url-status=dead}}

{{cite magazine|title=5 Plans to Head Off the Apophis Killer Asteroid|url=https://www.popularmechanics.com/space/deep-space/a1025/4201569/|archive-url=https://web.archive.org/web/20180612211352/https://www.popularmechanics.com/space/deep-space/a1025/4201569/|url-status=live|archive-date=June 12, 2018|magazine=Popular Mechanics|date=November 7, 2006|author=David Noland|access-date=March 14, 2021}}

{{cite news|url=http://cneos.jpl.nasa.gov/news/news146.html|title=Near-Earth Asteroid 2004 MN4 Reaches Highest Score To Date On Hazard Scale|first1=D.|last1=Yeomans|first2=S.|last2=Chesley|first3=P.|last3=Chodas|publisher=NASA/JPL CNEOS|date=December 23, 2004|access-date=January 31, 2024|quote=Today's impact monitoring results indicate that the impact probability for April 13, 2029, has risen to about 1.6%, which for an object of this size corresponds to a rating of 4 on the ten-point Torino Scale.}}

{{cite news|title=Possibility of an Earth Impact in 2029 Ruled Out for Asteroid 2004 MN4|publisher=NASA/JPL CNEOS|first1=D.|last1=Yeomans|first2=P.|last2=Chodas|first3=S.|last3=Chesley|url=http://cneos.jpl.nasa.gov/news/news148.html|date=December 27, 2004|access-date=January 31, 2024}}

{{cite news|title=Radar Observations Refine the Future Motion of Asteroid 2004 MN4|publisher=NASA's Near Earth Object Program Office|first1=P.|last1=Chodas|first2=S.|last2=Chesley|first3=J.|last3=Giorgini|first4=D.|last4=Yeomans|url=http://cneos.jpl.nasa.gov/news/news149.html|date=February 3, 2005|access-date=January 31, 2024}}

{{cite news|title=NASA Refines Asteroid Apophis' Path Toward Earth|publisher=NASA's Near Earth Object Program Office|first1=D.|last1=Brown|url=http://cneos.jpl.nasa.gov/news/news164.html|date=October 7, 2009|access-date=January 31, 2024}}

{{cite web|title=Sentry: Earth Impact Monitoring|publisher=NASA/JPL Center for NEO Studies|url=https://cneos.jpl.nasa.gov/sentry/|archive-url=https://web.archive.org/web/20210324054532/https://cneos.jpl.nasa.gov/sentry/|archive-date=March 24, 2021|url-status=dead|access-date=March 3, 2021}} (Use Unconstrained Settings to reveal 1979 XB with impact probability below 1e-6)

{{cite web|title=99942 Apophis (2004 MN4) Earth Impact Risk Summary|publisher=NASA/JPL Center for NEO Studies|url=http://neo.jpl.nasa.gov/risk/a99942.html|archive-url=https://web.archive.org/web/20130511010048/http://neo.jpl.nasa.gov/risk/a99942.html|archive-date=May 11, 2013|date=May 6, 2013|url-status=dead}} See also updated version at {{cite web|title=Sentry: Earth Impact Monitoring, Object Details|publisher=NASA/JPL Center for NEO Studies|access-date=February 8, 2021|archive-url=https://web.archive.org/web/20210208132353/https://cneos.jpl.nasa.gov/sentry/details.html#?des=99942|url=https://cneos.jpl.nasa.gov/sentry/details.html#?des=99942|archive-date=February 8, 2021|url-status=dead}}

{{cite web|title=Earth Impact Effects Program|publisher=Imperial College London / Purdue University|first1=R.|last1=Marcus|first2=H. J.|last2=Melosh|first3=G.|last3=Collins|url=http://impact.ese.ic.ac.uk/ImpactEffects/|date=2010|access-date=March 14, 2021}} (solution using 370 metres, 3000 kg/m³, 12.6 km/s, 45 degrees)

{{cite journal|last1=Reddy|first1=V.|last2=Sanchez|first2=J. A.|last3=Furfaro|first3=R.|last4=Binzel|first4=R. P.|last5=Burbine|first5=T. H.|last6=Le Corre|first6=L.|last7=Hardersen|first7=P. S.|last8=Bottke|first8=W. F.|last9=Brozovic|first9=M.|display-authors=4|title=Surface Composition of (99942) Apophis|journal=The Astronomical Journal|publisher=American Astronomical Society|volume=155|issue=3|date=March 5, 2018|issn=1538-3881|doi=10.3847/1538-3881/aaaa1c|page=140|arxiv=1803.05375|bibcode=2018AJ....155..140R|s2cid=78087061|doi-access=free}}

{{cite web|title=Horizons Batch for Apophis Orbital Elements for 2029-01-01 and 2030-01-01|publisher=JPL Horizons|url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Apophis%27&TABLE_TYPE=%27ELEMENTS%27&START_TIME=%272029-01-01%27&STOP_TIME=%272030-01-01%27&STEP_SIZE=%271%20year%27&CENTER=%27@Sun%27&OUT_UNITS=%27AU-D%27|access-date=July 31, 2022}}

{{cite web|title=Horizons Batch for Apophis @ 2029-Apr-13 21:45:03.5 showing 3-sigma uncertainty of ±3.3km|publisher=JPL Horizons|url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Apophis%27&START_TIME=%272029-Apr-13%2021:45:03%27&STOP_TIME=%272029-Apr-13%2021:45:04%27&STEP_SIZE=%272%27&QUANTITIES=%2720,39%27|archive-url=https://web.archive.org/web/20220131021056/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Apophis%27&START_TIME=%272029-Apr-13%2021:46%27&STOP_TIME=%272029-Apr-14%27&STEP_SIZE=%272%20days%27&QUANTITIES=%2720,39%27|archive-date=January 31, 2022|url-status=live|access-date=February 28, 2025}}

{{cite web|title=Horizons Batch for Apophis @ 2036-Mar-27 08:31 showing 3-sigma uncertainty of ±124566km|publisher=JPL Horizons|url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Apophis%27&START_TIME=%272036-Mar-27%2008:31%27&STOP_TIME=%272036-Mar-28%27&STEP_SIZE=%272%20days%27&QUANTITIES=%2720,39%27|archive-url=https://web.archive.org/web/20230710121335/https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Apophis%27&START_TIME=%272036-Mar-27%2008:30%27&STOP_TIME=%272036-Mar-28%27&STEP_SIZE=%272%20days%27&QUANTITIES=%2720,39%27|archive-date=July 10, 2023|url-status=live|access-date=February 28, 2025}}

{{cite web|title=Horizons Batch for Apophis @ 2051-Apr-20 02:05 showing 3-sigma uncertainty of ±237314km|publisher=JPL Horizons|url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Apophis%27&START_TIME=%272051-Apr-20%2002:05%27&STOP_TIME=%272051-Apr-21%27&STEP_SIZE=%272%20days%27&QUANTITIES=%2720,39%27|access-date=March 1, 2025}}

{{cite web|title=Horizons Batch for Apophis @ 2116-Apr-12 21:44 showing 3-sigma uncertainty of ±13 million km|publisher=JPL Horizons|url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Apophis%27&START_TIME=%272116-Apr-12%2021:44%27&STOP_TIME=%272116-Apr-13%27&STEP_SIZE=%272%20days%27&QUANTITIES=%2720,39%27|access-date=February 28, 2025}}

{{cite web|title=Horizons Batch for Apophis @ 2117-Oct-07 17:21 showing 3-sigma uncertainty of ±42 million km|publisher=JPL Horizons|url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Apophis%27&START_TIME=%272117-Oct-07%2017:21%27&STOP_TIME=%272117-Oct-08%27&STEP_SIZE=%272%20days%27&QUANTITIES=%2720,39%27|access-date=February 28, 2025}}

{{cite web|title=Horizons Batch for Apophis on 2068-Apr-12|publisher=JPL Horizons|url=https://ssd.jpl.nasa.gov/horizons_batch.cgi?batch=1&COMMAND=%27Apophis%27&START_TIME=%272068-Apr-12%27&STOP_TIME=%272068-Apr-13%27&STEP_SIZE=%272%20days%27&QUANTITIES=%2720,39%27|access-date=March 2, 2025}}

{{cite web|title=(99942) Apophis Ephemerides for 13 Apr 2029|publisher=NEODyS (Near Earth Objects — Dynamic Site)|url=https://newton.spacedys.com/neodys/index.php?pc=1.1.3.1&n=99942&oc=500&y0=2029&m0=4&d0=13&h0=18&mi0=0&y1=2029&m1=4&d1=14&h1=0&mi1=0&ti=10&tiu=minutes|access-date=August 19, 2018}}

{{cite web|title=99942 Apophis Ephemerides for April 2068|publisher=NEODyS (Near Earth Objects — Dynamic Site)|url=https://newton.spacedys.com/neodys/index.php?pc=1.1.3.1&n=99942&oc=500&y0=2068&m0=4&d0=1&h0=0&mi0=0&y1=2068&m1=4&d1=30&h1=0&mi1=0&ti=1.0&tiu=days|archive-url=https://web.archive.org/web/20210310182811/https://newton.spacedys.com/neodys/index.php?pc=1.1.3.1&n=99942&oc=500&y0=2068&m0=4&d0=1&h0=0&mi0=0&y1=2068&m1=4&d1=30&h1=0&mi1=0&ti=1.0&tiu=days|archive-date=March 10, 2021|url-status=live|access-date=May 9, 2019}}

{{cite web|title=MPEC 2004-Y70 : 2004 MN4|publisher=IAU Minor Planet Center|url=https://minorplanetcenter.net/mpec/K04/K04Y70.html|date=December 27, 2004}}

{{cite web|title=Scheduled Arecibo Radar Asteroid Observations|url=http://www.naic.edu/~pradar/sched.shtml|publisher=National Astronomy and Ionosphere Center}}

{{cite web|date=July 22, 2005|title=Schweickart Proposes Study of Impact Risk from Apophis (MN4)|publisher=NASA|author=Morrison, D.|author-link=David Morrison (astrophysicist)|url=http://nai.arc.nasa.gov/impact/news_detail.cfm?ID=161|access-date=October 8, 2009|url-status=dead|archive-url=https://web.archive.org/web/20090929071053/http://nai.arc.nasa.gov/impact/news_detail.cfm?ID=161|archive-date=September 29, 2009}}

{{cite web|title=Can NEAs be Grouped by Their Common Physical Characteristics?|last=Binzel|first=R. P.|work=Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology|publisher=aero.org|date=2007|url=http://www.aero.org/conferences/planetarydefense/2007papers/S1-8--Binzel-Brief.pdf|archive-url=https://web.archive.org/web/20120412135701/http://www.aero.org/conferences/planetarydefense/2007papers/S1-8--Binzel-Brief.pdf|archive-date=April 12, 2012|url-status=dead}}

{{cite magazine|title=Hawaii astronomers keep tabs on asteroid Apophis|magazine=Astronomy Magazine|url=https://astronomy.com/News-Observing/News/2011/03/Hawaii%20astronomers%20keep%20tabs%20on%20Asteroid%20Apophis.aspx|date=March 10, 2011|access-date=March 10, 2011}}

{{cite web|title=Asteroid 2004 MN4 will come scarily close to Earth on April 13, 2029, but it will not hit|publisher=Science@NASA|author=Morrison, D.|author-link=David Morrison|url=https://science.nasa.gov/science-news/science-at-nasa/2005/13may_2004mn4/|date=April 6, 2011}}

{{cite web|title=Apophis asteroid encounter in 2013 should help answer impact worries|work=USA Today ScienceFair|first=D.|last=Vergano|url=http://content.usatoday.com/communities/sciencefair/post/2010/11/apophis-asteroid-2013/1|date=November 10, 2010|access-date=November 10, 2010}}

{{cite web|title=The subtle effect of sunlight may turn the near-Earth asteroid Apophis toward Earth in 2068 . . . but chances for impact remain small.|publisher=Sky & Telescope|first=G.|last=Schilling|url=https://skyandtelescope.org/astronomy-news/apophis-impact-small-chance-2068/|date=October 27, 2020|access-date=November 1, 2020}}

{{cite web|title=99942 Apophis Ephemerides for 9 Jan 2013|publisher=NEODyS (Near Earth Objects — Dynamic Site)|url=https://newton.spacedys.com/neodys/index.php?pc=1.1.3.1&n=99942&oc=500&y0=2013&m0=01&d0=07&h0=0&mi0=0&y1=2013&m1=01&d1=25&h1=0&mi1=0&ti=3.0&tiu=hours|access-date=March 14, 2021}}

{{cite web|last1=deGrasse Tyson|first1=N.|title=Neil deGrasse Tyson — Death By Giant Meteor|url=https://www.youtube.com/watch?v=xaW4Ol3_M1o&t=165s|via=YouTube|date=March 12, 2008|access-date=March 14, 2021}}

{{cite web|title=2004 MN4 Earth Impact Risk Summary (computed on Dec 27, 2004)|work=The Cosmic Mirror|first=D.|last=Fischer|url=http://www.astro.uni-bonn.de/~dfischer/mirror/285neo041227.html|archive-url=https://web.archive.org/web/20050314032111/https://astro.uni-bonn.de/~dfischer/mirror/285neo041227.html|archive-date=March 14, 2005|url-status=dead|date=December 27, 2004|access-date=November 4, 2011}}

{{cite web|title=We Got it! The Story of Astronomers and Citizen Astronomers Catching Hazardous Apophis Asteroid over Colorado and Louisiana|publisher=SETI Institute|first=F.|last=Marchis|url=https://www.seti.org/we-got-it|archive-url=https://web.archive.org/web/20210310222038/https://www.seti.org/we-got-it|date=March 10, 2021|archive-date=March 10, 2021|url-status=live|access-date=March 13, 2021}}

{{cite web|title=99942 Apophis dynamical parameters|url=https://newton.spacedys.com/~neodys2/epoch//99942.eq1|publisher=NEODyS-2|date=March 14, 2021|access-date=March 14, 2021}}

{{cite web|title=Goldstone Radar Observations Planning: 99942 Apophis in 2021|url=https://echo.jpl.nasa.gov/asteroids/Apophis/apophis.2021.goldstone.planning.html|publisher=Jet Propulsion Laboratory|date=March 9, 2021|access-date=March 19, 2021}}

{{cite news|last1=Brown|first1=D.|last2=Wendel|first2=J.|last3=Agle|first3=D. C.|title=Scientists Planning Now for Asteroid Flyby a Decade Away|url=https://www.jpl.nasa.gov/news/news.php?feature=7390|date=April 29, 2019|work=NASA|access-date=April 29, 2019}}

{{cite journal|title=Asteroid Apophis set for a makeover|url=http://www.astronomy.com/asy/default.aspx?c=a&id=3434|first=B.|last=Cooke|journal=Astronomy Magazine|date=August 18, 2005|access-date=October 8, 2009|archive-url=https://archive.today/20120529114151/http://www.astronomy.com/en/sitecore/content/Home/News-Observing/News/2005/08/Asteroid%20Apophis%20set%20for%20a%20makeover.aspx|archive-date=May 29, 2012|url-status=dead}}

{{cite web|title=Preparing for asteroid Apophis {{!}} EarthSky.org|url=https://earthsky.org/space/preparing-asteroid-apophis-april-13-2029-passage|first=D.|last=Byrd|website=earthsky.org|date=April 30, 2019|access-date=May 1, 2019}}

{{cite web|title=The astronomical magnitude scale|url=http://www.icq.eps.harvard.edu/MagScale.html|work=International Comet Quarterly|access-date=January 19, 2021}}

{{cite web|title=Apophis Risk Assessment Updated|url=https://cneos.jpl.nasa.gov/news/news178.html|website=cneos.jpl.nasa.gov|date=February 21, 2013|archive-url=https://web.archive.org/web/20190408105438/https://cneos.jpl.nasa.gov/news/news178.html|archive-date=April 8, 2019|url-status=dead}}

{{cite web|title=Update notes: Apophis (Mar 2015)|url=https://cneos.jpl.nasa.gov/sentry/notes.html|website=Sentry: Earth Impact Monitoring, Operational Notes|publisher=NASA/JPL Center for NEO Studies|date=March 2, 2015|access-date=May 8, 2019|archive-url=https://web.archive.org/web/20170414081713/https://cneos.jpl.nasa.gov/sentry/notes.html|archive-date=April 14, 2017|url-status=live}}

{{cite journal|url=https://ui.adsabs.harvard.edu/abs/2020DPS....5221406T/abstract|title=Detection of Yarkovsky Acceleration of (99942) Apophis|author1=Tholen, D.|author2=Farnocchia, D.|date=October 2020|journal=Bulletin of the American Astronomical Society|volume=52|issue=6|pages=214.06|bibcode=2020DPS....5221406T}}

{{cite web|url=https://www.fr.de/wissen/asteroid-apophis-astronomie-generalprobe-forschende-erde-beruechtigt-asteroiden-90225775.html|title="Apophis": Gefährlicher Asteroid nähert sich der Erde – Letzte Chance für Forschende|date=March 4, 2021|access-date=March 4, 2021|language=de|author=Banner, T.|work=Frankfurter Rundschau|trans-title="Apophis": Hazardous asteroid approaches Earth – last chance for scientists}}

{{cite web|url=https://newton.spacedys.com/neodys/index.php?pc=2.1.2&o=C53&ab=0|title=C53-NEOSSat – Observations and residuals|publisher=NEODyS-2|access-date=March 4, 2021}}

{{cite web|url=https://iawn.net/obscamp/Apophis/apophis_gallery.shtml|title=99942 Apophis 2021 – Gallery|date=March 19, 2021|access-date=June 1, 2022|publisher=IAWN}}

{{cite web|last=Tanga|first=P.|title=Targeted Campaigns – Apophis 2021|url=https://asteroid-obs.oca.eu/foswiki/bin/view/Main/Campaigns|archive-url=https://web.archive.org/web/20210312194317/https://asteroid-obs.oca.eu/foswiki/bin/view/Main/Campaigns|date=March 10, 2021|access-date=March 12, 2021|archive-date=March 12, 2021|url-status=dead}}

{{cite web|url=https://www.asteroidoccultation.com/observations/Results/Reviewed/index.html|title=Asteroidal Occultation Reviewed Results for North America – 2021 Asteroidal Occultation Preliminary Results|date=March 8, 2021|access-date=March 12, 2021|website=asteroidoccultation.com|archive-url=https://web.archive.org/web/20210314170448/https://www.asteroidoccultation.com/observations/Results/Reviewed/index.html|archive-date=March 14, 2021|url-status=dead}}

{{cite web|url=https://lists.vvs.be/archives/list/planoccult@ls.vvs.be/thread/3V2PAXYJLI43S64VWWTCKC5MVS3BK6DV/|title=Reports of Apophis occultation 2021 Mar. 7 for our stations 3 and 4 near Oakdale, Louisiana (SwRI lines A28 and A30)|date=March 9, 2021|access-date=March 13, 2021|publisher=Verenigung veer Sterrenkunde}} (requires registration)

{{cite web|title=JPL Small-Body Database Browser: 99942 Apophis (2004 MN4)|type=last observation: March 8, 2021; arc: 16.98 years; JPL #206 solution date: 2021-Mar-09|url=https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=99942|archive-url=https://web.archive.org/web/20210311045729/https://ssd.jpl.nasa.gov/sbdb.cgi?sstr=99942|url-status=dead|date=March 9, 2021|archive-date=March 11, 2021|access-date=March 11, 2021}}

{{cite journal|title=Detection of the Yarkovsky Effect on 1998 SD9 from Optical Observations|author1=Bamberger, D.|author2=Wells, G.|doi=10.3847/2515-5172/aadf80|date=September 2018|journal=Research Notes of the AAS|volume=2|issue=3|page=164|bibcode=2018RNAAS...2..164B|s2cid=125805680|doi-access=free}}

{{cite journal|last1=Wee|first1=L. K.|last2=Goh|first2=G. H.|title=A geostationary Earth orbit satellite model using Easy Java Simulation|journal=Physics Education|publisher=IOP Publishing|volume=48|issue=1|date=December 14, 2012|issn=0031-9120|doi=10.1088/0031-9120/48/1/72|pages=72–79|arxiv=1212.3863|s2cid=119208827}}

{{cite web|first=J.|last=Giorgini|url=http://neo.jpl.nasa.gov/apophis/|archive-url=https://web.archive.org/web/20160115022151/http://neo.jpl.nasa.gov/apophis/|title=Predicting Apophis' Earth Encounters in 2029 and 2036|date=October 2007|archive-date=January 15, 2016|url-status=dead}}

{{cite news|url=https://www.bild.de/regional/berlin/weltuntergang-ausgerechnet-4178182.bild.html|title=Ich habe den Weltuntergang ausgerechnet!|newspaper=Bild|date=April 4, 2008|first=M.|last=Sauerbier|access-date=March 14, 2021|language=de|trans-title=I have calculated the apocalypse|archive-url=https://web.archive.org/web/20180809105514/https://www.bild.de/regional/berlin/weltuntergang-ausgerechnet-4178182.bild.html|archive-date=August 9, 2018|url-status=live}}

{{cite news|title=NASA refutes story of boy who predicted asteroid collision|url=http://www.cbc.ca/news/technology/nasa-refutes-story-of-boy-who-predicted-asteroid-collision-1.724724|publisher=CBC/Radio-Canada|date=April 16, 2008|access-date=November 8, 2015}}

{{cite web|url=http://afp.google.com/article/ALeqM5g6fIS_34_CxE8-vcC5GvbjD4MIOQ|title=German schoolboy, 13, corrects NASA's asteroid figures|access-date=April 16, 2008|archive-url=https://web.archive.org/web/20080420013749/http://afp.google.com/article/ALeqM5g6fIS_34_CxE8-vcC5GvbjD4MIOQ|archive-date=April 20, 2008|url-status=dead}}

{{cite web|url=http://www.nasa.gov/home/hqnews/2008/apr/HQ_08103_student_asteroid_calculations.html|title=NASA Statement on Student Asteroid Calculations|publisher=NASA|date=April 16, 2008|last=Brown|first=D.|archive-url=https://web.archive.org/web/20080501104959/https://www.nasa.gov/home/hqnews/2008/apr/HQ_08103_student_asteroid_calculations.html|archive-date=May 1, 2008|url-status=dead}}

{{cite web|url=http://neo.jpl.nasa.gov/apophis/apophis_unknown_bias.gif|title=99942 Apophis (2004 MN4)|website=neo.jpl.nasa.gov|access-date=August 9, 2017|archive-url=https://web.archive.org/web/20170302092856/http://neo.jpl.nasa.gov/apophis/apophis_unknown_bias.gif|archive-date=March 2, 2017|url-status=dead}}

{{cite web|url=https://www.nasa.gov/home/hqnews/2009/oct/HQ_09-232_Apophis_Update.html|first=D.|last=Brown|access-date=October 7, 2009|date=October 7, 2009|title=NASA Refines Asteroid Apophis' Path Toward Earth|archive-url=https://web.archive.org/web/20091009092704/http://www.nasa.gov/home/hqnews/2009/oct/HQ_09-232_Apophis_Update.html|archive-date=October 9, 2009|url-status=live}}

{{cite web|url=http://neo.jpl.nasa.gov/apophis/apophis_image7.html|title=Apophis Trajectory Change 2018–2036: Energy Reflection, Absorption, and Emission|first=J.|last=Giorgini|publisher=NASA|archive-url=https://web.archive.org/web/20071109141136/http://neo.jpl.nasa.gov/apophis/apophis_image7.html|archive-date=November 9, 2007|url-status=dead}}

{{cite web|first=R.|last=Schweickart|url=http://www.b612foundation.org/papers/wpdynamics.pdf|title=Threat Characterization: Trajectory dynamics (White Paper 39)|access-date=February 22, 2008|website=Figure 4, pp. 9. B612 Foundation|archive-url=https://web.archive.org/web/20080228181959/http://www.b612foundation.org/papers/wpdynamics.pdf|archive-date=February 28, 2008|url-status=dead}}

{{cite journal|title=Near Earth Object impact simulation tool for supporting the NEO mitigation decision making process|journal=Near Earth Objects|volume=236|page=477|date=2006|first=N. J.|last=Baileya|doi=10.1017/S1743921307003614|bibcode=2007IAUS..236..477B|doi-access=free}}

{{cite journal|first=M. P.|last=Paine|date=January 1999|url=http://mpainesyd.com/idisk/Public/paine_tsunami_asteroid99.pdf|title=The Threat is Out There|journal=Science of Tsunami Hazards|volume=17|issue=3|page=155|access-date=March 14, 2021|archive-url=https://web.archive.org/web/20150606044355/http://mpainesyd.com/idisk/Public/paine_tsunami_asteroid99.pdf|archive-date=June 6, 2015|url-status=live}}

{{cite news|first=P.|last=Rincon|title=US team wins asteroid competition|url=http://news.bbc.co.uk/2/hi/science/nature/7265608.stm|access-date=March 25, 2009|date=February 26, 2008}}

{{cite web|url=http://www.spacedaily.com/reports/Riding_an_asteroid_Chinas_next_space_goal_999.html|title=Riding an asteroid: China's next space goal|author=Yu Fei|agency=Xinhua News Agency|date=March 7, 2017|access-date=May 1, 2017}}

{{cite web|url=http://www.esa.int/SPECIALS/NEO/SEMZRZNVGJE_0.html|title=Don Quijote concept|website=esa.int|publisher=European Space Agency|archive-url=https://web.archive.org/web/20060904234133/http://www.esa.int/SPECIALS/NEO/SEMZRZNVGJE_0.html|archive-date=September 4, 2006|date=April 4, 2006|url-status=dead}}

{{cite news|last=Bartels|first=M.|title=NASA's OSIRIS-REx probe could make a 2nd stop at infamous asteroid Apophis|url=https://www.space.com/osiris-rex-asteroid-probe-could-visit-apophis-2029|access-date=January 28, 2021|work=Space.com|date=January 19, 2021}}

{{cite conference|title=OSIRIS-REx at Apophis: Opportunity for an Extended Mission|url=https://www.hou.usra.edu/meetings/apophis2020/pdf/2008.pdf|date=November 6, 2020|first1=D. S.|last1=Lauretta|author-link1=Dante Lauretta|first2=E. B.|last2=Bierhaus|first3=R. P.|last3=Binzel|first4=B. J.|last4=Bos|conference=Apophis T–9 Years: Knowledge Opportunities for the Science of Planetary Defense|conference-url=https://www.hou.usra.edu/meetings/apophis2020/}}

{{cite journal|url=http://www.esa.int/gsp/ACT/doc/MAD/pub/ACT-RPR-MAD-2006-(Acta)OptimalTrajectoriesForTheImpulsiveDeflectionOfNearEarthObjects.pdf|title=Optimal Trajectories for the Impulsive Deflection of NEOs|last1=Izzo|first1=D.|last2=Bourdoux|first2=A.|last3=Walker|first3=R.|last4=Ongaro|first4=F.|journal=Acta Astronautica|date=2006|doi=10.1016/j.actaastro.2006.02.002|bibcode=2006AcAau..59..294I|volume=59|issue=1–5|pages=294–300}}

{{cite web|title=Scenarios for Dealing with Apophis|url=http://www.aero.org/conferences/planetarydefense/2007papers/S3-4--Gennery-Paper.pdf|publisher=The Aerospace Corporation|access-date=July 18, 2008|archive-url=https://web.archive.org/web/20080827195229/http://www.aero.org/conferences/planetarydefense/2007papers/S3-4--Gennery-Paper.pdf|archive-date=August 27, 2008|url-status=dead}}

{{cite news|last=Isachenkov|first=V.|title=Russia may send spacecraft to knock away asteroid|publisher=Yahoo News|access-date=December 31, 2009|date=December 30, 2009|url=https://news.yahoo.com/s/ap/eu_russia_asteroid_encounter|archive-url=https://web.archive.org/web/20100102065122/http://news.yahoo.com/s/ap/eu_russia_asteroid_encounter|archive-date=January 2, 2010|url-status=dead}}

{{cite news|title=China Reveals Solar Sail Plan To Prevent Apophis Hitting Earth in 2036|work=Technology Review Physics arXiv Blog|access-date=March 14, 2021|date=August 18, 2011|url=http://www.technologyreview.com/blog/arxiv/27088/|archive-url=https://web.archive.org/web/20111126222934/http://www.technologyreview.com/blog/arxiv/27088/|archive-date=November 26, 2011|url-status=dead}}

{{cite news|title=Russia wants to target near-Earth objects with its ICBMs|work=TASS in foxnews.com|access-date=February 15, 2016|date=February 15, 2016|first=A.|last=Khoury|url=https://www.foxnews.com/tech/russia-wants-to-target-near-earth-objects-with-its-icbms}}

{{cite web|title=Rage Interview: We speak with id's Tim Willits about their new IP, Rage|website=Gamespot|url=https://www.gamespot.com/videos/rage-interview/2300-6176219/|first=T.|last=Winegarner|date=November 6, 2019}}

{{cite journal|title=Yarkovsky-driven impact risk analysis for asteroid (99942) Apophis|last1=Farnocchia|first1=D.|last2=Chesley|first2=S. R.|last3=Chodas|first3=P. W.|last4=Micheli|first4=M.|date=February 20, 2013|journal=Icarus|volume=224|issue=1|page=192|doi=10.1016/j.icarus.2013.02.020|arxiv=1301.1607|bibcode=2013Icar..224..192F|s2cid=119088923}}

{{cite web|title=Apophis' Yarkovsky acceleration improved through stellar occultation|url=https://www.cosmos.esa.int/web/gaia/iow_20210329|date=March 29, 2021|work=Gaia Image of the Week|publisher=European Space Agency (ESA)|access-date=November 27, 2021}}

{{cite web|title=Lifetime Achievement Award of the International Occultation Timing Association|url=https://www.asteroidoccultation.com/observations/Awards/Venable.html|date=2021|website=asteroidoccultation.com|publisher=International Occultation Timing Association|access-date=November 27, 2021}}

{{cite journal|title=Chasing the Shadow of (99942) Apophis|url=https://iota-es.de/JOA/JOA2021_3.pdf|year=2021|journal=Journal of Occultation Astronomy|volume=11|issue=3|pages=1–2, 24–29|access-date=November 27, 2021}}

{{cite web|title=2004 MN4 Earth Impact Risk Summary|publisher=NASA/JPL|url=http://neo.jpl.nasa.gov/risk/2004mn4.html|date=February 5, 2005|access-date=January 13, 2013|url-status=dead|archive-url=https://web.archive.org/web/20050206005155/http://neo.jpl.nasa.gov/risk/2004mn4.html|archive-date=February 6, 2005}}

{{cite web|title=99942 Apophis Earth Impact Risk Summary|publisher=NASA JPL|url=http://neo.jpl.nasa.gov/risk/a99942.html|date=October 18, 2005|access-date=January 13, 2013|url-status=dead|archive-url=https://web.archive.org/web/20051018181735/http://neo.jpl.nasa.gov/risk/a99942.html|archive-date=October 18, 2005}}

{{cite web|title=99942 Apophis (2004 MN4) Earth Impact Risk Summary|publisher=NASA/JPL|url=http://neo.jpl.nasa.gov/risk/a99942.html|date=July 1, 2006|access-date=January 13, 2013|url-status=dead|archive-url=https://web.archive.org/web/20060701215601/http://neo.jpl.nasa.gov/risk/a99942.html|archive-date=July 1, 2006}}

{{cite web|title=99942 Apophis (2004 MN4) Earth Impact Risk Summary|publisher=NASA/JPL|url=http://neo.jpl.nasa.gov/risk/a99942.html|date=August 5, 2006|access-date=January 13, 2013|url-status=dead|archive-url=https://web.archive.org/web/20060805063943/http://neo.jpl.nasa.gov/risk/a99942.html|archive-date=August 5, 2006}}

{{cite web|title=99942 Apophis (2004 MN4) Earth Impact Risk Summary|publisher=NASA/JPL|url=http://neo.jpl.nasa.gov/risk/a99942.html|date=May 6, 2013|access-date=March 13, 2021|url-status=dead|archive-url=https://web.archive.org/web/20130110015803/http://neo.jpl.nasa.gov/risk/a99942.html|archive-date=January 10, 2013}}

{{cite journal|title=Apophis Planetary Defense Campaign|first1=Vishnu|last1=Reddy|first2=Michael S.|last2=Kelley|first3=Jessie|last3=Dotson|first4=Davide|last4=Farnocchia|display-authors=etal|date=May 31, 2022|journal=The Planetary Science Journal|volume=3|issue=5|page=123|doi=10.3847/PSJ/ac66eb|bibcode=2022PSJ.....3..123R|s2cid=249227833|doi-access=free|hdl=10150/670423|hdl-access=free}}

{{cite journal|title=NEOWISE Observations of the Potentially Hazardous Asteroid (99942) Apophis|first1=Akash|last1=Satpathy|first2=Amy|last2=Mainzer|first3=Joseph R.|last3=Masiero|first4=Tyler|last4=Linder|display-authors=etal|date=May 31, 2022|journal=The Planetary Science Journal|volume=3|issue=5|page=124|doi=10.3847/PSJ/ac66d1|arxiv=2204.05412|bibcode=2022PSJ.....3..124S|s2cid=248118987|doi-access=free}}

{{cite web|title=Planetary Defense Exercise Uses Apophis as Hazardous Asteroid Stand-In|url=https://www.nasa.gov/feature/jpl/planetary-defense-exercise-uses-apophis-as-hazardous-asteroid-stand-in|date=May 31, 2022|publisher=NASA|editor=Tony Greicius|access-date=June 1, 2022}}

{{cite web|title=Neptune from the VLT with and without adaptive optics|url=https://www.eso.org/public/usa/images/eso1824b/|date=July 18, 2018|publisher=ESO|access-date=October 17, 2022}}

{{Cite news|url=https://www.bbc.com/future/article/20130117-doomsday-delayed|first=Quentin|last=Cooper|title=Apophis asteroid: Doomsday delayed... again|date=November 18, 2014|access-date=April 15, 2025|website=bbc.com}}

}}

{{Commons}}

• {{cite journal|arxiv=1404.5847|doi=10.1051/0004-6361/201423841|bibcode=2014A&A...566A..22M|title=Thermal infrared observations of asteroid (99942) Apophis with Herschel|year=2014|last1=Müller|first1=T. G.|last2=Kiss|first2=C.|last3=Scheirich|first3=P.|last4=Pravec|first4=P.|last5=o'Rourke|first5=L.|last6=Vilenius|first6=E.|last7=Altieri|first7=B.|journal=Astronomy & Astrophysics|volume=566|pages=A22|s2cid=119282830|display-authors=4}}
• [https://web.archive.org/web/20130317183119/http://apophisasteroid.net/ Apophis Asteroid]
• [http://meetingorganizer.copernicus.org/EPSC-DPS2011/EPSC-DPS2011-1212.pdf Asteroid Apophis orbit from recent observations], EPSC Abstracts Vol. 6, EPSC-DPS2011-1212, 2011, EPSC-DPS Joint Meeting 2011
• [http://www.brera.mi.astro.it/sormano/Apophis/Sormano_Apophis.html Diagrams and orbits of Apophis] (Sormano Astronomical Observatory)
• [https://web.archive.org/web/20200611222254/https://gravitysimulator.org/solar-system/apophis-2029-earth-encounter/ Interactive 3D gravity simulation of Apophis's 2029 Earth flyby]

Risk assessment

• [https://cneos.jpl.nasa.gov/doc/apophis/ Apophis Orbital Prediction Page at NASA JPL]
• [https://newton.spacedys.com/neodys/index.php?pc=1.1.0&n=99942 99942 Apophis page] from NEODyS
• [http://www.brera.mi.astro.it/sormano/mbpl.html MBPL – Minor Body Priority List (technical List) at Sormano Observatory]
• [http://www.brera.mi.astro.it/sormano/teca.html TECA – Table of Asteroids Next Closest Approaches to the Earth at Sormano Observatory]

NASA

• [https://web.archive.org/web/20041228072731/http://neo.jpl.nasa.gov/news/news148.html Possibility of an Earth Impact in 2029 Ruled Out for Asteroid {{Minor planet|2004 MN|4}}] (JPL)
• [https://cneos.jpl.nasa.gov/news/news149.html Radar Observations Refine the Future Motion of Asteroid {{Minor planet|2004 MN|4}}] (JPL)
• [https://web.archive.org/web/20041102064506/http://neo.jpl.nasa.gov/gif/mea-orbit-big.gif Animation explaining how impact risk is determined] from [https://web.archive.org/web/20160106045208/http://neo.jpl.nasa.gov/cgi-bin/ip?1 Impact Probability]
• {{JPL small body|id=99942}}

{{s-start}}

{{s-bef|before={{Minor planet link|(153814) 2001 WN|5}}}}

{{s-ttl|title=Large NEO Earth close approach
(inside the orbit of the Moon)|years=April 13, 2029}}

{{s-aft|after={{Minor planet link|2012 UE|34}}}}

{{end}}

{{Planetary defense}}

{{Minor planets navigator |99941 Lonniewege |number=99942 |(99943) 2005 AS2}}

{{Small Solar System bodies}}

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099942

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Category:Earth-crossing asteroids

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