C/2013 A1 (Siding Spring)

The comet was discovered on 3 January 2013 by professional astronomer Robert McNaught at the Siding Spring Observatory at Coonabarabran NSW Australia and received the official designation C/2013 A1.{{r|MPEC2013-A14}} It was named Siding Spring based on a tradition to identify the observatory that discovered it. Three images were obtained through the use of a CCD camera mounted on the Uppsala Southern Schmidt Telescope with a spherical mirror of 0.5 meters in diameter. Comet Siding Spring had an apparent magnitude of 18.4 to 18.6. At the time of its discovery, it was {{convert|7.2|AU|km mi|abbr=on|lk=on}} from the Sun.

Precovery images by the Catalina Sky Survey from 8 December 2012 were found quickly and announced with the discovery giving Comet Siding Spring a 29-day observation arc.{{r|MPEC2013-A14}} On 3 March 2013, Pan-STARRS precovery images from 4 October 2012 were announced that extended the observation arc to 148 days.{{r|mpc}}

{{multiple image|align=center

|title=Comet Siding Spring Mars flyby on 19 October 2014 (artist's concepts) |total_width=600 |width1=2560 |height1=1600 |image1=PIA18611-Mars-CometSidingSpringFlyby-20141009.jpg |caption1=Orbiters take cover from Comet Siding Spring during Mars flyby |width2=786 |height2=385 |image2=CometSidingSpring-HeadingTowardsMars-ArtistConcept-20141006.jpg|caption2=Mars as seen from Comet Siding Spring |width3=1080 |height3=668 |image3=Comet-SidingSpring-Passing-PlanetMars-On-20141019-ArtistConcept-20140905.jpg |caption3=Comet Siding Spring as seen from Mars }}

File:Animation of C／2013 A1 orbit.gif

Comet Siding Spring passed extremely close to Mars on 19 October 2014 at 18:28 ± 0:01 UTC.{{r|jpl1}} Initial observations by Leonid Elenin on 27 February 2013, suggested that it might pass {{cvt|0.000276|AU|km mi}} from the center of Mars.{{r|Elenin_2013b}} With an observation arc of 733 days, the nominal pass is {{cvt|0.000931|AU|km mi}} from the center-point of Mars and the uncertainty region shows that it would not come closer than {{cvt|0.000927|AU|km mi}}.{{r|jpl1}}

For comparison, Mars's outer moon Deimos orbits it at a distance of {{cvt|0.00016|AU|km mi}}. Due to the uncertainty region, there was the possibility that it could pass Mars as far away as {{cvt|0.000934|AU|km mi}}. It actually passed by at a distance of {{cvt|140496.6|±|4.0|km|mi}},{{r|Farnocchia_2016}} at a relative velocity of {{cvt|56|km/s|mi/s}}.{{r|jpl1}} As seen from Mars, C/2013 A1 peaked at approximately apparent magnitude −6.{{r|twitter-20141028}}{{dubious|date=March 2023}}

{{multiple image|align=center|caption_align=center|title=Comet Siding Spring encounter with Mars, 19 October 2014|total_width=600 |width1=1920 |height1=1080 |image1=Mars-C2013A1SidingSpring-Orbits-20141019.png |caption1=Projected position of Comet Siding Spring and its closest approach to Mars |width2=1655 |height2=1516 |image2=PIA17833-CometSidingSpring-C2013A1-MarsEncounter-20140128.png |caption2=Comet Siding Spring encounter }}

File:PIA18593-Mars-CometSidingSpring-NEOWISE-20140728.jpg

The main body of the comet's tail was projected to miss Mars by some 10 Mars diameters.{{r|Ye_2014}} As a result, only higher-than-average-velocity meteoroid dust, ejected earlier in the approach of the comet, allow for impacts on Mars, its moons, and orbiting spacecraft. Dust particles ejected from the nucleus of the comet, at more than double the expected velocity when the comet was 3 AU from the Sun, could reach Mars approximately 43 to 130 min after the closest approach of the comet.{{r|Farnocchia_2014}} There is a possibility for millimeter- to centimeter-size particles released more than 13 AU from the Sun, however, this is considered unlikely,{{r|Farnocchia_2014}} although massive ejections from farther out have been deduced.{{r|Sekanina_2014}}

In 2013 it was thought possible that Comet Siding Spring would create a meteor shower on Mars or be a threat to the spacecraft in Mars orbit. Studies in 2014 showed the threat to orbiting spacecraft to be minimal. The greatest threat would be about 100 minutes after closest approach. Mars passed about {{cvt|27000|km|mi}} from the comet's orbit around 20:10 UT.{{r|Kelley_2014}}

The coma of the comet is projected to more than double the amount of hydrogen in the high atmosphere for a period of several tens of hours and to warm it by about 30 K for a few hours—the combination increasing the effect of atmospheric drag on the Mars Reconnaissance Orbiter and MAVEN spacecraft causing a measurable increase in orbital decay because of atmospheric ram pressure.{{r|Yelle_2014}} These spacecraft will be approaching Mars to minimum altitudes of 250 km and 150 km and orbital periods of 3 and 4 hours, respectively. The amount of drag cannot be narrowed down greatly until the production rate of the comet is known, but it could be from 1.6 to 40 times normal drag. MAVEN, in particular, also has instruments to observe any changes to the gas composition of the atmosphere. The closer moon of Mars, Phobos, orbits far higher, at a minimum distance of {{cvt|9234.42|km|mi}},{{cite web

|date = 30 September 2003

|title = Mars: Moons: Phobos

|url = http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mar_Phobos&Display=Facts

|publisher = NASA

|access-date = 2 December 2013

|archive-url = https://web.archive.org/web/20131019162634/http://solarsystem.nasa.gov/planets/profile.cfm?Object=Mar_Phobos&Display=Facts

|archive-date = 19 October 2013

|url-status = dead

|df = dmy-all

}} more than 10 times the height of Mars's atmosphere.{{r|ESA_20121115}}

Estimates for the diameter of the nucleus have varied from {{cvt|1|–|50|km|mi}},{{r|Elenin_2013a|NASA-20130327}} but now the nucleus is known to be only approximately {{cvt|400–700|m|ft}} in diameter, roughly the diameter of asteroid {{mpl|2010 XG|11}} that approached Mars on 29 July 2014.{{r|jpl2}} Based on early upper-limit size estimates, the resulting upper-limit energy of a hypothetical impact with Mars was 24 billion megatons.{{r|Elenin_2013a|Bell_2013}} The diameter of such a hypothetical impact crater would be roughly ten times the diameter of the comet's nucleus.{{r|Elenin_2013a}} A 700-meter impactor would create around a {{cvt|7|–|10|km|mi}} crater.

The odds of an impact with Mars were 1-in-1250 in March 2013,{{r|Elenin_2013c}} 1-in-2000 in late March 2013,{{r|NASA-20130327}} 1 in 8000 by April 2013,{{r|CBS2013-04}} and 1-in-120,000 by 8 April 2013.{{r|NASA2013-081}} The 8 April 2013 JPL Small-Body Database 3-sigma solution was the first estimate to show that the minimum approach by Comet Siding Spring would miss Mars.{{r|jpl1|Farnocchia_2014}}

MAVEN detected an intense meteor shower.{{r|JPL141107}} Comet Siding Spring has a rotation period of approximately 8 hours.{{r|JPL141107}}{{clarify|date=August 2023|reason=Clarify how the comet's rotation period would be relevant to its effects on Mars.}} Debris from Comet Siding Spring added a temporary, but strong layer of ions to Mars's ionosphere (the first time such a phenomenon has been observed on any planet), and 85 tonnes of cometary dust were vaporized high in Mars's atmosphere. Magnesium, iron, and other metals were observed to have been deposited.{{r|NYT-20141107}} An observer on the surface would have seen a few tens of meteors during the plane crossing.{{r|Farnham_2014}}

During the flyby of Mars at a proximity of {{cvt|140000|km|mi}}, Comet Siding Spring's magnetic field, generated by its interaction with the solar wind, caused a violent turmoil that lasted for several hours, long after its flyby. Its coma washed over Mars with the dense inner coma, reaching or almost reaching the planet's surface. The cometary magnetic field temporarily merged with and overwhelmed Mars' weak magnetic field.{{r|Espley_2015}}

File:PIA17833-CometSidingSpring-C2013A1-NEOWISE-20140128.jpg on 16 January 2014]]

As seen from Earth, on 19 October 2014, Mars was in the constellation Ophiuchus, near globular cluster NGC 6401, and 60 degrees from the Sun. Mars and C/2013 A1 were {{convert|1.6|AU|e6km e6mi|abbr=unit}} from Earth. As of October 2014, C/2013 A1 had an apparent magnitude of roughly 11 and was the third-brightest comet in the sky at that time.{{r|Yoshida141011|MPEC2014-T44}} At an apparent magnitude of 0.9, Mars was estimated to be about 11,000 times brighter than the diffuse-looking comet with a low-surface brightness.{{efn|Apparent magnitude: $(\backslash sqrt[5]\{100\})^\{11-0.9\}\backslash approx\; 10964$}} To observe C/2013 A1 visually from Earth would have required a telescope with an optical mirror at least {{cvt|0.2|m|in}} in diameter. By November 2014 the comet had dimmed to magnitude 11.6 and was only around the fifth-brightest comet in the sky.{{r|Yoshida141102}}

Mars and Comet Siding Spring were visible to the STEREO-A spacecraft during the 2014 encounter.{{r|STEREO-HI2}} In orbit around Mars were the spacecraft Mars Reconnaissance Orbiter, 2001 Mars Odyssey, ESA's Mars Express, MAVEN, and the Indian Mars Orbiter Mission (Mangalyaan). The last two missions had arrived less than one month before the closest approach of C/2013 A1 to Mars. All these artificial satellites may have been exposed to potentially damaging particles.{{r|Moorhead_2014|NASA-20140128}} The level of exposure will not be known for months, but NASA had taken several "precautionary measures" as it prepared to study C/2013 A1.{{r|NASA-20140725}} Two key strategies to lessen the risk were to place the orbiters on the opposite side of Mars at the time of the highest risk and to orient the orbiters so that their most vulnerable parts were not in the line of impact.{{r|NASA-20140128}} On the ground, the Curiosity and Opportunity rovers obtained images as well. Results from the observations will be discussed during a special session "Comet C/2013 A1 Siding Spring at Mars" at the 2014 AGU Fall Meeting in San Francisco on 18 December 2014.{{Update inline|date=September 2015}}

{{multiple image

| align = center

| direction = horizontal

| image1 = Mars Fleet and Comet Siding Spring.webm

| width1 = 200

| alt1 =

| caption1 = Comet Siding Spring passes Mars on 19 October 2014.

| image2 = Sun view of Comet Siding Spring and the Mars orbiting fleet.ogg

| width2 = 200

| alt2 =

| caption2 = Orbiters hide as Comet Siding Spring passes Mars.

}}

{{multiple image

| align = center

| direction = horizontal

| image1 = MAVEN and Comet Siding-Spring encountering Mars.webm

| width1 = 200

| alt1 =

| caption1 = MAVEN and Comet Siding Spring encounter Mars.

| image2 = MAVEN and Comet Siding-Spring encountering Mars fixed cam.webm

| width2 = 200

| alt2 =

| caption2 = MAVEN and Comet Siding Spring encountering Mars – fixed-camera view.

| image3 = Mars orbiters landers rovers during Comet Siding Spring.webm

| width3 = 200

| alt3 =

| caption3 = Comet Siding Spring – watched by several landers and orbiting spacecraft.

}}

{{wide image|Comet Siding Spring Close Approach.png|600px|align-cap=center|Closest approach of Comet Siding Spring to Mars – maximum and minimum distances noted}}

{{wide image|Comet-C2013A1-SidingSpring-NearMars-Hubble-20141019.jpg|600px|align-cap=center|Close encounter of Comet Siding Spring with the planet Mars
(composite image; Hubble ST; 19 October 2014).}}

{{Gallery

| align = center

| title =

| width = 180

| height = 140

|Image:Comet C-2013 A1 Siding Spring flyby from Mars Orbiter.jpg|Images taken by the Mars Reconnaissance Orbiter of Comet Siding Spring on 19 October 2014

|Image:Cometa C2014 A1 en su acercamiento al planeta Marte.JPG|Image by the Observatorio de la Asociación Entrerriana de Astronomía from Earth on 19 October 2014

||Image by a 90-mm (3.5-inch) telescope from Earth on 19 October 2014, about 9 hours after closest approach.

}}

{{Gallery

| align = center

| title =

| width = 180

| height = 140

|Image:MER Opportunity Comet Siding Spring Blink.gif|Images taken by the Opportunity Rover of Comet Siding Spring from the Martian surface on 19 October 2014

|Image:PIA18591-MarsOpportunityRover-CometSidingSpringFlyby-20141019.jpg|Image taken by the Opportunity Rover of Comet Siding Spring from the Martian surface on 19 October 2014

|Image:PIA18592-MarsOpportunityRover-CometSidingSpringFlyby-20141019.jpg|Image taken by the Opportunity Rover of Comet Siding Spring from the Martian surface on 19 October 2014

}}

{{wide image|PIA19043-MarsCuriosityRover-CometSidingSpring-20141019.gif|600px|align-cap=center|The Curiosity rover views Comet C/2013 A1 during flyby on 19 October 2014.}}

{{Notelist}}

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| publisher=NASA

| work=Swift satellite

| url=http://www.nasa.gov/content/goddard/nasas-swift-satellite-tallies-water-production-of-mars-bound-comet

| access-date=20 June 2014 }}

{{cite web

| date=28 February 2013

| title=Hit or Miss? Either way, NASA/STEREO-A spacecraft has a ring-side seat of "Siding Spring v's Mars" next year

| publisher=Sungrazing Comets

| first=Bill | last=Thompson

| url=http://twitpic.com/c7jfp3

| archive-url=https://web.archive.org/web/20130303051916/http://twitpic.com/c7jfp3 | archive-date=3 March 2013 | url-status=live }}

{{cite web

| date=12 April 2013

| title=Comet to Make Close Flyby of Red Planet in October 2014

| publisher=NASA/JPL

| first=David C. |last=Agle

| url=http://www.jpl.nasa.gov/news/news.php?release=2013-081

| archive-url=https://web.archive.org/web/20130308140413/http://www.jpl.nasa.gov/news/news.php?release=2013-081 | archive-date=8 March 2013 | url-status=live }}

{{cite web

| date=1 April 2013

| title=Mars vs. comet in 2014: Scientists prepare for red planet sky show

| work=CBS News

| url=https://www.cbsnews.com/news/mars-vs-comet-in-2014-scientists-prepare-for-red-planet-sky-show/

| archive-url=https://web.archive.org/web/20130402213942/http://www.cbsnews.com/8301-205_162-57577242/mars-vs-comet-in-2014-scientists-prepare-for-red-planet-sky-show/ | archive-date=2 April 2013 | url-status=live }}

{{cite web

| date=6 December 2013 | work=New Scientist

| last=Grossman | first=Lisa

| title=Fiercest meteor shower on record to hit Mars via comet

| url=https://www.newscientist.com/article/dn24715-fiercest-meteor-shower-on-record-to-hit-mars-via-comet.html

| archive-url=https://web.archive.org/web/20131212093435/http://www.newscientist.com/article/dn24715-fiercest-meteor-shower-on-record-to-hit-mars-via-comet.html | archive-date=12 December 2013 | url-status=live }}

{{cite web

| url=http://cometcampaign.org/karl/siding-spring-risk-assessment

| title=Comet Siding Spring: Risk Assessment

| first=Karl |last=Battams

| date=2 August 2014

| access-date=12 August 2014}}

{{cite news

|last=Kaufmann

|first=Marc

|title=A Celestial Traveler Closes on Mars

|url=https://www.nytimes.com/2014/08/05/science/space/celestial-traveler-closing-on-mars.html

|date=4 August 2014

|work=The New York Times

|access-date=4 August 2014}}

{{cite web

|url = http://scully.cfa.harvard.edu/cgi-bin/returnprepeph.cgi?d=c&o=CK13A010

|title = Elements and Ephemeris for C/2013 A1 (Siding Spring)

|publisher = IAU Minor Planet Center

|archive-url = https://web.archive.org/web/20141012120502/http://scully.cfa.harvard.edu/cgi-bin/returnprepeph.cgi?d=c&o=CK13A010

|archive-date = 12 October 2014

|url-status = dead

|df = dmy-all

|access-date = 8 February 2013

}}

{{cite web

|date=11 October 2014

|title=Weekly Information about Bright Comets (2014 Oct. 11: South)

|first=Seiichi |last=Yoshida

|publisher=aerith.net

|url=http://www.aerith.net/comet/weekly/20141011s.html

|access-date=11 October 2014}}

{{cite web

|date=2 November 2014

|title=Weekly Information about Bright Comets (2014 Nov. 1: North)

|first=Seiichi |last=Yoshida

|publisher=aerith.net

|url=http://www.aerith.net/comet/weekly/20141101n.html

|access-date=10 November 2014}}

{{cite web

|date=6 October 2014

|title=MPEC 2014-T449 : Observations and Orbits of Comets

|publisher=IAU Minor Planet Center

|url=http://www.minorplanetcenter.net/mpec/K14/K14T44.html

|access-date=11 October 2014}} (lookup as CK13A010)

{{cite web

|url=http://www.jpl.nasa.gov/news/news.php?feature=4366

|title=Mars Spacecraft Reveal Comet Flyby Effects on Martian Atmosphere

|date=7 November 2014

|publisher=JPL }}

{{cite web

|title=How to determine the orbit of a comet?

|publisher=esa

|quote=It took 44 days of observation to achieve even a semblance of an orbit determination – one that was still all over the place

|date=2014-03-07

|url=http://blogs.esa.int/mex/2014/03/07/how-to-determine-the-orbit-of-a-comet/

|accessdate=2022-01-08 }}

}}

{{Commons category}}

• {{JPL small body}}
• [http://scully.cfa.harvard.edu/cgi-bin/returnprepeph.cgi?d=c&o=CK13A010 C/2013 A1 (Siding Spring)] – Elements and Ephemeris – Minor Planet Center
• [http://www.aerith.net/comet/catalog/2013A1/2013A1.html C/2013 A1 (Siding Spring)] – Seiichi Yoshida @ Aerith.net
• [http://cometbase.net/en/observation/listObserv/85 C/2013 A1 (Siding Spring)] – CometBase
• [http://www.virtualtelescope.eu/2014/10/19/comet-c2013-a1-siding-spring-planet-mars-history-unique-image/ C/2013 A1 Siding Spring and Mars ] – Virtual Telescope Project (19 October 2014)
• [http://mars.nasa.gov/comets/sidingspring/ NASA – Official WebSite] – Comet Siding Spring.
• [https://www.youtube.com/watch?v=Oq8lEKAY_fI NASA – VIDEO (02:19)] – Overview of Comet Flyby of Mars (9 October 2014).
• [https://www.youtube.com/watch?v=yICO-Fy3RQ0 NASA – VIDEO (56:15)] – Press Briefing of Comet Flyby of Mars (9 October 2014).
• [http://www.iceinspace.com.au/forum/attachment.php?s=c104f3d68b3549220fa18b9427f7ef2b&attachmentid=171685 Comet C/2013 A1 and Mars] – 80mm f4 refractor/Pentax K-5 (17 October 2014).
• [http://s727.photobucket.com/user/Rob_Kau/media/C2013A116amp17Oct2014200mmtextsmall.jpg.html Comet C/2013 A1 and Mars] – 200mm f5.6 telephoto/Canon 650D (composite; 17 October 2014).
• [http://www.brera.mi.astro.it/sormano/C2013A1/C2013A1.html Comet C/2013 A1 and Mars] – Sormano Astronomical Observatory (19 October 2014).
• [http://planetary.s3.amazonaws.com/assets/images/4-mars/2014/20141103_15599878605_1be102f3bc_o.jpg Comet C/2013 A1 passes Mars] – Curiosity rover view (enlarged upper-left; 19 October 2014).
• [http://apod.nasa.gov/apod/ap141020.html Comet C/2013 A1 passes Mars] – NASA APOD (20 October 2014).
• [https://web.archive.org/web/20141030044929/http://www.latestspacenews.com/comet-siding-spring-c-2013-a1-seen-next-to-mars.html Comet C/2013 A1 passes Mars] – Hubble Space Telescope (22 October 2014).
• [http://www.planetary.org/blogs/emily-lakdawalla/2014/11031353-seven-mars-spacecraft.html Comet C/2013 A1 passes Mars] – Collection of images (posted 3 November 2014).

{{Comets}}

{{Mars}}

{{2013 in space}}

{{2014 in space}}

{{DEFAULTSORT:Siding Spring, 2013 A1}}

Category:Non-periodic comets

20130103

Category:Discoveries by SSS

Category:Comets in 2013

Category:Comets in 2014

20141019

2013A01

Category:Articles containing video clips

Category:Predicted impact events