# Is Mars Mostly Flat? **URL:** \ **Category:** Factual Questions\ **Created:** [May 27, 2008, 11:55pm UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832 "2008-05-27T23:55:08Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\ **Post date:** [May 27, 2008, 11:55pm UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/1 "2008-05-27T23:55:08Z")
All the pictures sent back show a flat horizon, maybe a few low hills. So, outside of the giant shield volcanos, is Mars bereft of mountains? If Mars never had plate tectonics, did all of the heavy elements just settle, leaving only light silicate rocks on the surface? And, if Mars once had oceans, what do the bottoms of these basins look like today? ---
**Author:** ![WoodenTaco](https://avatars.discourse-cdn.com/v4/letter/w/45deac/32.png) [@WoodenTaco](https://boards.straightdope.com/u/WoodenTaco)\ **Post date:** [May 27, 2008, 11:59pm UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/2 "2008-05-27T23:59:27Z")
[Here](http://www.google.com/mars/) is an elevation map of Mars. It’s far from flat. [Olympus Mons](http://en.wikipedia.org/wiki/Olympus_Mons) is the tallest known mountain in the solar system! ---
**Author:** ![Crescend](https://avatars.discourse-cdn.com/v4/letter/c/b9bd4f/32.png) [@Crescend](https://boards.straightdope.com/u/Crescend)\ **Post date:** [May 28, 2008, 12:10am UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/3 "2008-05-28T00:10:17Z")
It’s not that Mars is flat, but rather the places where our probes land are flat. If you’re trying to send a probe to land on Mars, you’d much rather land it someplace nice and flat and not worry about dropping into a canyon or hitting a mountain along the way. ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [May 28, 2008, 12:45am UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/4 "2008-05-28T00:45:49Z")
Given increased knowledge of Martian surface conditions, I’m not sure if this is still valid, but I recall reading some time ago that the Hellas basin, in Mars’s southern hemisphere is depressed sufficiently below mean surface level (“sea level,” as it were) that it is the one place off Earth in the solar system where liquid water could theoretically exist (albeit only on “warm” afternoons in the southern summer, when the temperature would be above local melting point – but the point being that on most of Mars’s surface, ice would sublimate to water vapor like CO2 from dry ice; Hellas is the closest thing on the real Mars to a “dead sea bottom of Barsoom.” Valles Marineris, largest fluvial valley known, also deserves mention in discussing areomorphology (i.e. Martian "geo-"morphology). ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [May 28, 2008, 1:03am UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/5 "2008-05-28T01:03:12Z")
[QUOTE=WoodenTaco] [Here](http://www.google.com/mars/) is an elevation map of Mars. It’s far from flat. [Olympus Mons](http://en.wikipedia.org/wiki/Olympus_Mons) is the tallest known mountain in the solar system! [/QUOTE] It is a bitch to climb too. Mt. Everest is for pussies. ---
**Author:** ![squeegee](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/squeegee/32/14537_2.png) [@squeegee](https://boards.straightdope.com/u/squeegee)\ **Post date:** [May 28, 2008, 1:48am UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/6 "2008-05-28T01:48:13Z")
[QUOTE=Shagnasty] It is a bitch to climb too. Mt. Everest is for pussies. [/QUOTE] Actually, according to that Wiki article, the average slope is 2.5 degrees. You could pretty much mountain bike to the summit (given an inhuman ability to hold your breath for the 170-mile ride). Wow – Olympus Mons is about as wide as New Mexico! ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [May 28, 2008, 3:05am UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/7 "2008-05-28T03:05:36Z")
[QUOTE=Polycarp] I’m not sure if this is still valid, but I recall reading some time ago that the Hellas basin, in Mars’s southern hemisphere is depressed sufficiently below mean surface level (“sea level,” as it were) that it is the one place off Earth in the solar system where liquid water could theoretically exist… [/QUOTE] Zero elevation on Mars was defined as the elevation at which atmospheric pressure was 6.1173 millibars. At that pressure you’ll get liquid water at any temperature above 273.16°K ([the triple point](http://en.wikipedia.org/wiki/Triple_point)). Nowdays they use laser altimetry to determine elevations on Mars, but I don’t think they’ve significantly changed the zero datum\*. If you look at **WoodenTaco** ’s map you’ll see that the Hellas basin is indeed quite far below “sea level”, but so is much of the northern hemisphere. The Phoenix lander touched down [in an area where liquid water may have been common until quite recently:](http://64.233.167.104/search?q=cache:Fnuhqqwd2k0J:www.lpi.usra.edu/meetings/polar2006/pdf/8076.pdf+phoenix+%22triple+point%22+mars+water&hl=en&ct=clnk&cd=3&gl=us&client=firefox-a) > [@](#): > > Modern liquid water at the Martian surface, should it occur, would be an important factor in the potential habitability of the environment. In the current epoch, conditions in the Northern Plains never reach the triple point pressure and temperature, the point of thermodynamic stability of pure liquid water. Unlike at the corresponding latitudes in the Southern hemisphere, in the low elevation Northern Plains, pressure is above the triple point but the solar flux is not strong enough to warm the surface above 0C. However, climate modeling studies [3, 4] show that the Northern plains experience strong variations in the incident solar insolation due to variation of orbital parameters. Importantly, the solar longitude of perihelion and the obliquity both vary on Mars, and the solar flux at the Phoenix landing site has varied by over a factor of three during the last million years. Only 25,000 years ago, solar forcing at the Phoenix landing site was strong enough that triple point conditions were exceeded up to 50 days a year[4] and many such warm periods have occurred in the last million years. * * * \*Of course what with the large seasonal fluctuations in pressure on Mars, the significance of that datum with respect to the possibilty of liquid surface water at any given time and temperature is sort of dubious. ---
**Author:** ![Ponch8](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ponch8/32/9883_2.png) [@Ponch8](https://boards.straightdope.com/u/Ponch8)\ **Post date:** [May 28, 2008, 3:15am UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/8 "2008-05-28T03:15:04Z")
[QUOTE=WoodenTaco] [Olympus Mons](http://en.wikipedia.org/wiki/Olympus_Mons) is the tallest known mountain in the solar system! [/QUOTE] I noticed that in this Wikipedia article, they give the latitude and longitude of the mountain. How was the arbitrary 0 degrees of longitude chosen for Mars? It’s not like they have any Greenwich Observatories over there. ---
**Author:** ![Askance](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/askance/32/8281_2.png) [@Askance](https://boards.straightdope.com/u/Askance)\ **Post date:** [May 28, 2008, 3:49am UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/9 "2008-05-28T03:49:46Z")
[QUOTE=ralph124c] And, if Mars once had oceans, what do the bottoms of these basins look like today? [/QUOTE] [Here](http://www.planetary.org/news/2006/0315_Mars_Odyssey_Team_Creates.html)’s a link to a .mov file of a virtual fly-though of Mars’ answer to the Grand Canyon. As with Mt Olympus, it is hugely bigger than the Earth equivalent - it’s as long as the USA is wide, and deeper than Mt Everest is high. ---
**Author:** ![Bryan\_Ekers](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bryan_ekers/32/183_2.png) [@Bryan\_Ekers](https://boards.straightdope.com/u/Bryan_Ekers)\ **Post date:** [May 28, 2008, 3:54am UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/10 "2008-05-28T03:54:38Z")
[QUOTE=Shagnasty] It is a bitch to climb too. Mt. Everest is for pussies. [/QUOTE] Gravity being only one-third that of Earth, it might not be all that taxing. ---
**Author:** ![Ike\_Witt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ike_witt/32/283_2.png) [@Ike\_Witt](https://boards.straightdope.com/u/Ike_Witt)\ **Post date:** [May 28, 2008, 2:23pm UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/11 "2008-05-28T14:23:54Z")
[QUOTE=Bryan Ekers] Gravity being only one-third that of Earth, it might not be all that taxing. [/QUOTE] Maybe so, but getting to base camp is tough. ---
**Author:** ![exastris](https://avatars.discourse-cdn.com/v4/letter/e/b38774/32.png) [@exastris](https://boards.straightdope.com/u/exastris)\ **Post date:** [May 28, 2008, 2:50pm UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/12 "2008-05-28T14:50:05Z")
[QUOTE=Ponch8] I noticed that in this Wikipedia article, they give the latitude and longitude of the mountain. How was the arbitrary 0 degrees of longitude chosen for Mars? It’s not like they have any Greenwich Observatories over there. [/QUOTE] It’s an arbitrary crater within a crater (Airy-0 in the Sinus Meridiani area). I think Schiaparelli was the first to map Mars using this as the 0, and it just stuck. It’s been nailed down more precisely as we’ve gotten better visuals on the area. ---
**Author:** ![wolfman](https://avatars.discourse-cdn.com/v4/letter/w/a8b319/32.png) [@wolfman](https://boards.straightdope.com/u/wolfman)\ **Post date:** [May 28, 2008, 2:51pm UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/13 "2008-05-28T14:51:42Z")
[QUOTE=squeegee] Actually, according to that Wiki article, the average slope is 2.5 degrees. You could pretty much mountain bike to the summit (given an inhuman ability to hold your breath for the 170-mile ride). [/quote] ☹ SO much for that Olympus mons sledding trip I’ve been planning. ---
**Author:** ![toadspittle](https://avatars.discourse-cdn.com/v4/letter/t/c0e974/32.png) [@toadspittle](https://boards.straightdope.com/u/toadspittle)\ **Post date:** [May 28, 2008, 2:55pm UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/14 "2008-05-28T14:55:29Z")
[QUOTE=squeegee] Actually, according to that Wiki article, the average slope is 2.5 degrees. You could pretty much mountain bike to the summit (given an inhuman ability to hold your breath for the 170-mile ride). [/QUOTE] What a brilliant idea. True, current pressure suits are pretty bulky, but I imagine, in the future, a mountain bike might be a handy means of transportation on Mars! Beats having nuclear-powered rovers. ---
**Author:** ![gonzomax](https://avatars.discourse-cdn.com/v4/letter/g/e8c25b/32.png) [@gonzomax](https://boards.straightdope.com/u/gonzomax)\ **Post date:** [May 28, 2008, 3:12pm UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/15 "2008-05-28T15:12:51Z")
According to Friedman even Mars is flat. ---
**Author:** ![KneadToKnow](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kneadtoknow/32/3999_2.png) [@KneadToKnow](https://boards.straightdope.com/u/KneadToKnow)\ **Post date:** [May 28, 2008, 3:30pm UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/16 "2008-05-28T15:30:39Z")
[QUOTE=Crescend] It’s not that Mars is flat, but rather the places where our probes land are flat. If you’re trying to send a probe to land on Mars, you’d much rather land it someplace nice and flat and not worry about dropping into a canyon or hitting a mountain along the way. [/QUOTE] Just ask Val Kilmer, et al. ---
**Author:** ![HeyHomie](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/heyhomie/32/207_2.png) [@HeyHomie](https://boards.straightdope.com/u/HeyHomie)\ **Post date:** [May 28, 2008, 4:53pm UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/17 "2008-05-28T16:53:25Z")
[QUOTE=WoodenTaco] [Olympus Mons](http://en.wikipedia.org/wiki/Olympus_Mons) is the tallest known mountain in the solar system! [/QUOTE] What would be REALLY cool would be to see an artist’s impression of what Olympus Mons would look like to an observer on the [Martian] ground. ---
**Author:** ![muldoonthief](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muldoonthief/32/3188_2.png) [@muldoonthief](https://boards.straightdope.com/u/muldoonthief)\ **Post date:** [May 28, 2008, 4:59pm UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/18 "2008-05-28T16:59:21Z")
[QUOTE=toadspittle] What a brilliant idea. True, current pressure suits are pretty bulky, but I imagine, in the future, a mountain bike might be a handy means of transportation on Mars! Beats having nuclear-powered rovers. [/QUOTE] You have to be careful of the trade embargo & taxes though. (Nickel to the first person who gets that reference) ---
**Author:** ![Tristan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tristan/32/18058_2.png) [@Tristan](https://boards.straightdope.com/u/Tristan)\ **Post date:** [May 28, 2008, 5:47pm UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/19 "2008-05-28T17:47:57Z")
[QUOTE=muldoonthief] You have to be careful of the trade embargo & taxes though. (Nickel to the first person who gets that reference) [/QUOTE] Ah, but if you are smart enough to rig up a beacon to retrieve them from floating in space in the first place, you’ll be able to get around the fee’s and suchlike. ps- can I buy a flatcat with my nickel? ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [May 28, 2008, 6:05pm UTC](https://boards.straightdope.com/t/is-mars-mostly-flat/450832/20 "2008-05-28T18:05:18Z")
[QUOTE=HeyHomie] What would be REALLY cool would be to see an artist’s impression of what Olympus Mons would look like to an observer on the [Martian] ground. [/QUOTE] [Here’s one](http://www.spaceprime.com/olympus-mons.htm). (Olympus Mons is the distant rounded moutain, not the closer more rugged one.) I can’t vouch for its accuracy, though. [Here’s another](http://www.space-art.co.uk/pages-en/diagrams/Olympus-Mons.htm), but the top looks very odd - almost as if it was based on terrain mapping with missing data? [Next page](https://boards.straightdope.com/t/is-mars-mostly-flat/450832.md?page=2)