User:Chrisjj/Mars Ed

The surface gravity of Mars is 38% that of Earth. Although microgravity is known to cause health problems such as muscle loss and bone demineralization,{{cite journal |last=Fong, MD |first=Kevin |title=The Strange, Deadly Effects Mars Would Have on Your Body |url=https://www.wired.com/opinion/2014/02/happens-body-mars/ |date=12 February 2014 |journal=Wired |accessdate=2014-02-12 }}{{cite web |url=https://science.nasa.gov/science-news/science-at-nasa/2001/ast02aug_1/ |title=Gravity Hurts (so Good) |publisher=NASA |year=2001 }} it is not known if Martian gravity would have a similar effect. The Mars Gravity Biosatellite was a proposed project designed to learn more about what effect Mars' lower surface gravity would have on humans, but it was cancelled due to a lack of funding.{{cite web |title=Mars Mice |url=https://science.nasa.gov/science-news/science-at-nasa/2004/20jan_marsmice/ |work=science.nasa.gov |year=2004 }}

Due to the lack of a magnetosphere, solar particle events and cosmic rays can easily reach the Martian surface.{{cite web |url=https://science.nasa.gov/science-news/science-at-nasa/2001/ast31jan_1/ |title=The Solar Wind at Mars |date=January 31, 2001 |first=Tony |last=Phillips |publisher=NASA}}{{cite news | title=What makes Mars so hostile to life? | date=January 7, 2013 | url=http://www.bbc.co.uk/science/0/20915340 | work=BBC News }}{{cite journal | title=The impact of Mars geological evolution in high energy ionizing radiation environment through time | journal=Planetary and Space Science – Eslevier | date=November 2012 | first1=A. | last1=Keating | first2=P. | last2=Goncalves | volume=72 | issue=1 | pages=70–77 | doi=10.1016/j.pss.2012.04.009 | bibcode=2012P&SS...72...70K }}

Atmospheric pressure on Mars is far below the Armstrong limit at which people can survive without pressure suits. Since terraforming cannot be expected as a near-term solution, habitable structures on Mars would need to be constructed with pressure vessels similar to spacecraft, capable of containing a pressure between 30 and 100 kPa. The atmosphere is also toxic as most of it consists of carbon dioxide (95% carbon dioxide, 3% nitrogen, 1.6% argon, and traces totaling less than 0.4% of other gases including oxygen.

This thin atmosphere does not filter out ultraviolet sunlight, which causes instability in the molecular bonds between atoms. For example, ammonia (NH₃) is not stable in the Martian atmosphere and breaks down after a few hours.{{cite news |last=Whitehouse |first=David |date=July 15, 2004 |url=http://news.bbc.co.uk/2/hi/3896335.stm |title=Dr. David Whitehouse – Ammonia on Mars could mean life |publisher=BBC News |accessdate=August 14, 2012}}

Also due to the thinness of the atmosphere, the temperature difference between day and night is much larger than on Earth, typically around 70 °C (125 °F).{{cite web |url=http://cab.inta-csic.es/rems/index.htm |title=Mars Weather |publisher=Centro de Astrobiología |date=2015 |accessdate=May 31, 2015 |url-status=dead |archiveurl=https://archive.today/20151025050810/http://cab.inta-csic.es/rems/index.htm |archivedate=October 25, 2015 |df=mdy-all }} However, the day/night temperature variation is much lower during dust storms when very little light gets through to the surface even during the day, and instead warms the middle atmosphere.

Water on Mars is scarce, with rovers Spirit and Opportunity finding less than there is in Earth's driest desert.{{cite web |title=Why is Mars So Dry? |url=https://www.universetoday.com/9303/why-is-mars-so-dry/ |website=Universe Today |date=16 February 2004 |accessdate=26 November 2018}}{{cite journal |last=Hecht |first=M. H. |year=2002 |title=Metastability of Liquid Water on Mars |journal=Icarus |volume=156 |issue=2 |pages=373–386 |doi=10.1006/icar.2001.6794|bibcode = 2002Icar..156..373H }}{{cite web |last1=Webster |first1=Guy |last2=Brown |first2=Dwayne |title=NASA Mars Spacecraft Reveals a More Dynamic Red Planet |url=http://www.jpl.nasa.gov/news/news.php?release=2013-361&1#1 |date=10 December 2013 |work=NASA |accessdate=2014-03-02 }}

The climate is much colder than Earth, with mean surface temperatures between {{convert|186|and|268|K|C F|abbr=on}} (depending on the season and latitude).{{cite web |last=Hamilton |first=Calvin |title=Mars Introduction |url=http://www.solarviews.com/eng/mars.htm }}{{cite web |last=Elert |first=Glenn |title=Temperature on the Surface of Mars |url=http://hypertextbook.com/facts/2001/AlbertEydelman.shtml |date= }} The lowest temperature ever recorded on Earth was 184 K (−89.2 °C, −128.6 °F) in Antarctica.

Because Mars is about 52% farther from the Sun, the amount of solar energy entering its upper atmosphere per unit area (the solar constant) is only around 43.3% of what reaches the Earth's upper atmosphere.{{cite journal|url=http://discovermagazine.com/1992/sep/marsinearthsimag105|title=Mars, in Earth's Image |volume=13| issue=9| pages=70 |journal=Discover Magazine |accessdate=12 June 2015| bibcode=1992Disc...13...70K| last1=Kluger| first1=J. |year=1992}} However, due to the much thinner atmosphere, a higher fraction of the solar energy reaches the surface.{{cite book |url=http://www.uapress.arizona.edu/onlinebks/ResourcesNearEarthSpace/resources30.pdf |title=Atmospheric Effects on the Utility of Solar Power on Mars| url-status=dead|archiveurl=https://web.archive.org/web/20160305054458/http://www.uapress.arizona.edu/onlinebks/ResourcesNearEarthSpace/resources30.pdf| archivedate=2016-03-05| bibcode=1993rnes.book..845H| year=1993| last1=Haberle| first1=R. M.| last2=McKay| first2=C. P.| last3=Pollack| first3=J. B.|last4=Gwynne| first4=O. E.|last5=Atkinson|first5=D. H. |last6=Appelbaum| first6=J.|last7=Landis| first7=G. A.|last8=Zurek| first8=R. W. |last9=Flood| first9=D. J.}}{{Cite journal|bibcode=1957SvA.....1..547S|title=1957SvA.....1..547S Page 547| volume=1 |pages=547 |journal=Harvard.edu |last1=Sharonov| first1=V. V. |year=1957}} The maximum solar irradiance on Mars is about 590 W/m² compared to about 1000 W/m² at the Earth's surface; optimal conditions on the Martian equator can be compared to those on Devon Island in the Canadian Arctic in June.{{cite web |title=Sunlight on Mars – Is There Enough Light on Mars to Grow Tomatoes? |url=https://www.firsttheseedfoundation.org/resource/tomatosphere/background/sunlight-mars-enough-light-mars-grow-tomatoes/ |website=first the seed foundation |accessdate=26 November 2018}}

Global dust storms are common throughout the year and can cover the entire planet for weeks, blocking sunlight from reaching the surface.{{cite book| author=Viorel Badescu| title=Mars: Prospective Energy and Material Resources |url=https://books.google.com/books?id=BnPE37Ms5awC&pg=PA83| year=2009| publisher=Springer Science & Business Media| isbn=978-3-642-03629-3| page=83}}{{cite web| url=http://tomatosphere.org/teachers/guide/grades-8-10/mars-agriculture|title=Teachers guide – Sunlight on mars – Tomatosphere|author=Tomatosphere|work=tomatosphere.org|accessdate=12 June 2015|url-status=dead| archiveurl=https://web.archive.org/web/20150623152330/http://tomatosphere.org/teachers/guide/grades-8-10/mars-agriculture| archivedate=23 June 2015}} This has been observed to cause temperature drops of 4 °C (7 °F) for several months after the storm.{{cite journal | first1=Lori K. | last1=Fenton | first2=Paul E. | last2=Geissler | first3=Robert M. | last3=Haberle | title=Global warming and climate forcing by recent albedo changes on Mars | date=2007 | journal=Nature | volume=446 | doi=10.1038/nature05718 | url=http://humbabe.arc.nasa.gov/~fenton/pdf/fenton/nature05718.pdf | pages=646–649 | pmid=17410170 | issue=7136 | bibcode=2007Natur.446..646F | url-status=dead | archiveurl=https://web.archive.org/web/20070708011126/http://humbabe.arc.nasa.gov/~fenton/pdf/fenton/nature05718.pdf | archivedate=July 8, 2007 | df=mdy-all }} In contrast, the only comparable events on Earth are infrequent large volcanic eruptions such as Krakatoa which threw large amounts of ash into the atmosphere in 1883, causing a global temperature drop of around 1 °C (2 °F). Perhaps more importantly, these storms affect electricity production from solar panels for long periods, as well interfering with communications with Earth.{{cite web |title=Opportunity Hunkers Down During Dust Storm |url=https://www.nasa.gov/feature/jpl/opportunity-hunkers-down-during-dust-storm |website=NASA |date=8 June 2018 |accessdate=26 November 2018}}

Mars has no rain and virtually no clouds, so although cold, it is permanently sunny (apart from during dust storms). This means solar panels can always operate at maximum efficiency on dust-free days. And Mars' orbit is more eccentric than Earth's, increasing temperature and solar constant variations over the course of the Martian year.

The Martian soil is toxic due to relatively high concentrations of chlorine and associated compounds which are hazardous to all known forms of life.{{cite web |title=Mars covered in toxic chemicals that can wipe out living organisms, tests reveal |url=https://www.theguardian.com/science/2017/jul/06/mars-covered-in-toxic-chemicals-that-can-wipe-out-living-organisms-tests-reveal |website=The Guardian |accessdate=26 November 2018}}{{cite web |title=Toxic Mars: Astronauts Must Deal with Perchlorate on the Red Planet |url=https://www.space.com/21554-mars-toxic-perchlorate-chemicals.html |website=space.com |accessdate=26 November 2018}}

Although there are some extremophile organisms that survive in hostile conditions on Earth, including simulations that approximate Mars, plants and animals generally cannot survive the ambient conditions present on the surface of Mars.{{cite web |url=http://library.thinkquest.org/12145/lifeon.htm |title= Can Life exist on Mars? |work= Mars Academy |publisher=ORACLE-ThinkQuest |date= | archiveurl = https://web.archive.org/web/20010222154617/http://library.thinkquest.org/12145/lifeon.htm | archivedate = February 22, 2001}}