New evidence of (transient) liquid water on Mars!

By Phil Plait | April 12, 2010 12:14 pm

Does liquid water still flow on Mars?

We know that in the distant past — like, a billion years ago — liquid water was abundant on Mars. We also know that water currently exists on Mars in the form of ice, sometimes just below the surface (where even small meteor impacts can reveal it). But can there still be liquid water flowing on Mars, even if only for a very, very short time?

Maybe. Just maybe.


This HiRISE image shows a small region of a Martian crater named Russel (click to access much bigger versions of it). There are a lot of sand dunes in it, and as you can see in the lower left, many gullies as well. These gullies were obviously carved by something moving downslope. Sometimes, these gullies can form due to the presence of dry ice: frozen carbon dioxide, which is abundant on Mars. In the summer, as temperatures warm, the dry ice turns into a gas, dislodging material and letting it roll downhill. It’s thought that quite a few gullies on Mars are formed this way (as well as very dramatic avalanches).

But these Russell Crater gullies are different. They do seem to form at higher elevations, near the tops of dunes, as you’d expect. But there are also weird dark spots near these locations, which are poorly understood. The gullies seem to be constrained in their width; they don’t get broader downslope. Mind you, these are super-hi-res images; the gullies shown here are only a few meters across, if even that! You could easily hop across them if you were strolling across the Red Planet’s surface.

The gullies do widen where two tributaries meet, which is exactly as you’d expect from flowing material. That’s probably clearer in this picture of the same region but taken at a different time:


But the really weird thing is how the gullies end. If this were just sand flowing because it was disrupted by dry ice evaporating, you’d expect to see a fan-shaped formation where the gullies terminate downslope. That’s the natural way flowing sand comes to a halt, by spreading out and forming those big triangles. But these gullies don’t do that. Instead, they just kinda stop. The gullies suddenly end in an abrupt narrowing of the trench, as if the material that’s moving is being reabsorbed by the surface underneath it.

That is certainly not what you expect from solid material like sand flowing downhill. It’s far more like the way an actual flowing liquid behaves. Because of this a team of German scientists studying this data think this may be more evidence that water can exist as a liquid on the surface of Mars, at least for short periods, time enough to flow downhill a bit. So we’re talking seconds or minutes here, not years, but still. Holy Haleakala.

[Edited to add: I neglected to mention originally that the length of these gullies has been seen to grow between the times the images were taken, meaning that whatever is flowing down these dunes is doing so right now. This isn’t some long-ago phenomenon; it happened a few weeks ago!]

Liquid water on the surface of Mars can’t stick around long; even at those low temperatures it will boil away from the low atmospheric pressure, or freeze rapidly. So having any liquid at all is really pretty amazing. But it raises lots of other questions, not the least of which are where does it come from, and why the heck is it liquid at all? You’d expect the water under the surface, if that’s what’s causing this, to be frozen; we see lots of that on Mars. So why is this liquid? Did something happen to liquify it (and it’s a pretty short list of what could do that), or is it liquid already (like in an underground aquifer or a hot spring) and just happened to break through the surface to flow for a short, glorious time?

The only way to know for sure is to keep looking. These images are a red flag for scientists, an alarm raised that we need to keep digging around, to keep our eyes open, and to pay attention to what we’re seeing. There’s a whole lot that Mars is trying to tell us. All we have to do is listen.

CATEGORIZED UNDER: Astronomy, Pretty pictures, Science
MORE ABOUT: gullies, HiRISE, Mars, water

Comments (54)

  1. Jeff in Tucson

    Kayaking anyone?

  2. And everywhere there is water, at least on this planet, there is life. And Mars?

  3. Hmm… You might want to ask the kids at Bowie Base One about that whole water thing, Phil.

    If there is water on Mars, do you really want to go mucking about with it?

  4. Pareidolius

    What would heat a hot spring on a geologically dead planet?

  5. @Pareidolius, are you a liquid water denier?

    It could be from heating from the Sun or maybe radioactive decay of some element.

  6. Wow, this reminds me of when I did a study of Mars in high school where we got to tell THEMIS where to take pictures to support our theories about water – we took four images (two IR and two Visible light). MSIP is a fantastic program through ASU that gets students excited about science in a very real way – getting to tell a satellite orbiting another planet exactly where to take pictures is an incredible experience. I’m finishing up my senior year of college now, and I still have the poster printout of our image on my wall.

    Also, that tricksy phenomenon I was already familiar with because of my hacking on NASA World Wind, and one that was well-explained by one Phil Plait in a couple of blog posts, is screwing with me…try as I might, I can only see worms ūüėõ

    By the way, here are our images, you can see my high school (W.F. West) in the description:
    Fortunately, it looks like the program is still going:

  7. Jeff

    To know if it is water underground that emerges shortly, I would ask, what are the temperatures and pressures below the ground here, say 1 meter, enough to allow the water to come out temporarily.

  8. Anyone up for a Martian Hot Tub party? ūüėÄ

  9. dWhisper

    Could the energy released by flowing or collapsing sand, or similarly images avalanches, cause enough heat release to form liquid water? The bigger gap to me seems to be that ice melting at those pressures should evaporate almost immediately, close enough that it’d look like sublimation unless really scrutinized.

    If this is water, that’s a huge shift in our view of the planet, and the biggest pointer we’ll get on where we should send a probe next.

  10. cbranch

    Regarding the ends of the gullies, and the way they just kind of stop: reminds me of the tracks of snowballs rolling down a hill and then stopping when they get to a point where the grade is not so steep. Of course then you might expect to see the snowball sitting there at the end of the track… anyway I’m sure brighter minds than mine have already considered this – just saying what it looks like to a non-expert in the field…

  11. Utakata

    Off of aside…

    …I think those images of Mars are beautiful and breath taking. But I can’ help but wonder if I would be disappointed when I get to walk around there. Not to mention my footprints would ruin dunes that have been sculptured for thousands of years. :(

  12. mars looks like a very promising place to colonize.
    Water looks abundant… and I think we have a lot of chances to find life there.

    So why are we not excited enough to go there already?

    Thanks again HiRISE, the coolest camera in the universe!

  13. Gary Ansorge

    It doesn’t have to be liquid water. It might be liquid hydrogen peroxide which boils at 150 degrees C.. Wiki doesn’t give the vapor pressure, but a higher boiling point generally means the vapor pressure is higher than water so it could remain liquid, for a while, at the low pressure on Mars.

    I’m not enough of a chemist to know if H2O2 could be produced inorganically on Mars, though there is R&D work ongoing to create it from rare earth catalysts. A 50% solution of H2O2 and H2o melts at about -61 degrees C.

    ,,,or maybe it’s just petroleum(Hello Exxon!).

    Gary 7

  14. Flavio

    Ok we have the next landing site for a mission!!!

  15. Torbjörn Larsson, OM

    Please tell me again – why do we have to wait on Curiosity?

    What would heat a hot spring on a geologically dead planet?

    Excellent – a geologically dead planet means that the detected methane on Mars for sure is due either to serpentinization from liquid water, or directly from life.

    I’m glad we got that riddle solved so easily.

  16. I thought it was just seeing not listening. ¬¬

  17. 24601

    could it be carbonated water, fizzing out of the ground as the co2 thaws and opens a path?

  18. If it is H2O2 would that mean the Martians are all blondes.

  19. katesisco

    Interesting! Origination from the TOP of ridge and flowing down. Water flows down due to gravity–but doesn’t perforce appear at the TOP of hill, mountain, whaterever but can, at least on Earth. Sounds like something solid, other than H2O.

  20. cgauthier

    And everywhere there is water, at least on this planet, there is life. And Mars?

    Life on Earth began in water, at one or more isolated locations, then spread to fill the rest of Earth’s water over a long time period.

    The presence of life, as we know it, requires water, but the presence of water doesn’t require life, at all.

    Mars could very well have been sopping wet and lifeless.

  21. jcm

    These images can be potentially pareidolius (pareidolia).

  22. MoonShark

    Why are people throwing around the term “geologically dead planet” when Phil has clearly showed us images of landslides, avalanches, and now gullies?

    At least one paper (2003) says it’s active…

  23. SpeedTek

    I was pretty sure that I read at one point that any water on mars would have a very high salt concentration in it, like a think brine. My science may be off, but I do believe that would change both the vapor pressure and freezing point.. a possiblity!

  24. Gary Ansorge

    18. Davidlpf

    Only if they washed their hair with it on Saturday nights.

    23. MoonShark

    What we mean by geologically active is quakes, volcanos, tectonic plates moving around. Stuff happening on the surface is not geological.

    24. SpeedTek

    Good call. Unfortunately, most salt water still freezes at the temps on Mars.
    From Wiki answers:
    “The freezing point of salt water varies depending on how much salt is in the water. For example, water that is 3500 parts per million salt (avg. amount in seawater) will freeze around -2 degrees celsius (28 degrees F). Water with an extreme amount of salt in it, like in some lake waters in Death Valley CA, with 300,000 ppm, will freeze at -20 to -30 degrees C (-4 to -20 degrees F). ”

    A 50% solution of H2O2 and H2O stays liquid down to -52 C.(221 K)
    “Mean Temperature at Solid Surface 186 to 268 K”(from NASA)

    Gary 7

  25. C. Redulous

    But Spike Psarris categorically told me that water is IMPOSSIBLE on the surface of Mars.
    He wouldn’t be wrong with God on his side would he?

  26. SpeedTek

    25. Gary Ansorge

    I do not think it is as much of an issue that the water stays frozen, but how long it will stay liquid before it sublimates. The atmospheric pressure on mars ranges from 6 to 10 millibars (compared to 1013.25 millibars on Earth), quite a big difference. I’m curious on how salt content effects sublimation pressures.

    But all things being equal if a sub-surface deposit of brine/water ice is warmed above its freezing temperature, and it is in the right position, it will begin to flow as a liquid. With the atmospheric temperature so low, it will still boil away, but not instantly. The channels we see could be carved out by the flow of water, albiet boiling water.

  27. PanchoLibre

    i really can’t believe that water would actually flow down only one side of those mountains! it looks like the ridge tops are dotted with boulders that have been exposed by erosion — my guess is wind and sand in the wind. even with a thin atmosphere, there are of course sandstorms that carry enough force to slowly eat away at even the hardest of rocks!

    the prevailing wind carries over the mountaintop and pushes sand, pebbles, and possibly even boulders down from the ridge line. they roll downhill and eventually get buried in the sand near the base of the gully. the trails they form flow together and end suddenly.

    Phil – as distinctive as sand flow deltas look, so would liquid of any kind leave a distinct pattern at the ends of the flow paths! to me, these tracks look more like wind and rocks than water.

    tell me if you disagree. these are just my two cents… and the HiRISE images are fantastic – thanks!

  28. Steve Paluch

    Clearly evidence of giant space worms.

  29. ethanol

    -Gary, Speedtek;

    I believe I read something about the potential for strong perchlorate salt solutions remaining liquid under those conditions. Remember that phoenix unexpectedly found significant concentrations of perchlorate in the soil. I found a source that gives the vapor pressure of a saturated sodium perchlorate solution @ 0 C as .427 kPa; well below martian atmospheric pressure, and I know that perchlorate solutions have significantly depressed freezing points (although I can’t find the value right now). Concentrated H2O2 solutions are probably not an option because they decompose so readily in the presence many metals and probably wouldn’t last long in martian soil.

  30. Brian Too

    @18. Davidlpf,

    No, that cannot possibly be right. While there are blondes on Mars, there are also women of every hair colour there. If 50’s sci-fi taught me anything, it’s that there are beautiful Amazons awaiting us!

    28. Steve Paluch,

    Not just giant space worms. Shai-Hulud (sandworms)!

    I wonder if the beautiful Martian Amazons ride the sandworms around?

  31. Dean

    Well, I guess it can’t be AGW ūüėČ

  32. 10. cbranch

    That’s a great idea worth investigating. If there are CO2 snowballs, then they might sublimate at the end of their trail.

  33. Russell Kramer

    I’m not exactly an exo-chemist, but everything I know about Mars suggests the pressure and temperature at its surface make liquid water impossible. I’m guessing this liquid is a chemical other than water, and there are a number to choose from that can exist on the surface of Mars.

  34. Bruce

    Carbon dioxide is abundant on Mars?!? GLOBAL WARMING!!! Send Al Gore over there to tax the Martians!

  35. Thameron

    Salty mud maybe?

  36. Michael Kingsford Gray

    Am I alone in thinking that the first photo is of a chocolate cephalopod?

  37. Loony Eachus

    “Carbon dioxide is abundant on Mars?!? GLOBAL WARMING!!! Send Al Gore over there to tax the Martians!”

    You’ve obviously fallen for the Martianothropic Global Warming scam! CO2 just can’t be a green house gas. It JUST can’t be because I’m ignorant of science!

  38. Those gullies are obviously not the kind created by airflow (like we see in sand dunes on Earth) so liquid seems the obvious answer but it occurred to me that a very heavy gas (in relation to the atmosphere) could create gullies of the same shape.

    What would be nice now is to observe changes in the shape of one of these gullies, which would let us know what time of year and potentially more precisely what temperatures this liquid or heavy gas exists at.

  39. Larry

    News that water (a) was once present on Mars and (b) perhaps flowed on the surface of Mars is no longer news. Got it. Alas, I think NASA’s (and Phil I don’t mean to include you here) continuing insistence on claiming evidence of water on Mars as news really reflects the lack of an ability to do new science.

  40. Ryan H

    martian ski slopes… the Breck of the red planet, if you will…

  41. Steve

    Brines have a -much- lower freezing point. You can have liquid water at -20F. The surface of Mars in the tropics easily reaches 80*F during the day. I’m not sure why these things are so quickly forgotten. Further, the thin Martian air can only hold so much water. At saturation, you don’t get further net evaporation.

    The idea of Mars being geologically dead is a theory, not a proven fact. We’ve yet to land a seismometer net, for one thing (a very strange omission, IMHO)

    I would suggest that areas with these on-going gully formation events would be a good target for a MER-class rover.

  42. Chemical Engineer

    Steve – that’s not the way saturation works. The molecules in the atmosphere don’t “hold” the water vapor. The lower the pressure of the atmosphere, the faster the water will evaporate. At sufficiently low pressures (below the vapor pressure of water at a given temperature), liquid water will boil and you’ll lose it all very quickly. Of course, the boiling will suck a lot of energy out of the system because the enthalpy of vaporization is very large, meaning you’ll typically be left with solid and gaseous water, but no liquid.

  43. MadScientist

    I wonder if the surface emissivity would show some contrast between the water flows (when water is flowing anyway) and the surrounding areas. Then again if there’s liquid water there’s water vapor and perhaps a microwave radiometer would be a more suitable instrument.

  44. Taxorgian

    As others already mentioned, some other liquid sounds way more plausible here. Is there any significant quantity of ammonia on Mars? The pressure/temperature range on Mars seems much nicer for it and I know that it isn’t uncommon in more distant planets.

  45. Some Aki

    I don’t want to spoil the party, but there must be a connection between the dark spots (in this case blue because of the false color) and the gullies. I happened to look at the broad picture here:

    , and can only see these peculiar spots where the supposed “water flow” is. It really looks like a liquid flow, but is it really water or some different fluid?

    These spots are to me very similar to some other places on mars, where they are known to form during spring, when the carbon dioxide evaporates. Is it possible, considering the temperatures and pressure on mars, composition of the soil, that this is some carbonated mix of water and CO2 with some added salt maybe? I am saying this because maybe, just maybe, CO2 and water at some strange conditions which we don’t see here on Earth (mainly pressure) can form such a liquid on Mars so it can flow for some time on the surface? Atmospheric pressure is the key here, as David Bowie says here:

  46. veskebjorn

    This piece perfectly illustrates a critical problem in much of what passes for scientific discussion. Author Phil Platt says: “We know that in the distant past ‚ÄĒ like, a billion years ago ‚ÄĒ liquid water was abundant on Mars. We also know that water currently exists on Mars in the form of ice, sometimes just below the surface (where even small meteor impacts can reveal it).”

    1.) “We” don’t “know…liquid water was abundant on Mars…” This statement is a hypothesis based on scanty evidence. Further observations and research may prove it wrong. And exactly what range of quantities does Platt mean by the vague adjective “abundant”?

    2.) Similarly, “we also know that [ice] currently exists on Mars,” is another hypothesis. Similarly, Platt does not quantify the amount of the hypothesized ice, where it might be located on Mars, and how much of it is “just below the surface.”

    Please go back through the piece and count up all the “cans” and “coulds” and “seems” and “mights” and every other qualifying adjective and adverb. Then put your science hat on and try to filter the real science from the speculation.

    What you are left with is the following: An otherwise unidentified “team of German[s]” has examined some unidentified number of photos of the surface of Mars and hypothesized that some changes in features may indicate the presence of liquid water.

    Or may not…this statement is almost purely speculative.

    Whenever I see writing such as this, I am reminded of Mark Twain’s observation in “Life on the Mississippi”: “There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.”

  47. veskebjorn (50): The evidence is hardly “scanty”. Have you not paid any attention that past few years? The evidence of ancient water on Mars is overwhelming. A veritable flood of it, you might say.

    By the way, it’s Plait, not Platt. Accusing people of sloppy research can be very ironic sometimes.

  48. veskebjorn

    Dear Mr. Plait,

    Yes I have paid attention for the past few years, and much longer than that. I am so old that I was an adult when the first non-Earth-based obvservation of Mars was made. I have paid attention to speculations about Mars since the mid 1950’s.

    For decades, based on telescopic observations by the famous astronomer Percival Lowell, many folks thought Mars had canals. Lowell was wrong then, and his successors may be wrong now. The existence of “abundant” water on Mars today is a speculative idea, based almost entirely on space-based observations, a handful of “landers,” and a few acres of surface-based exploration. I regard these observations as “scanty.”

    Seven or eight or nine years ago, a scientist from NASA in Mountain View, California, told the Santa Cruz astronomy club that there was *some* exciting new evidence and interpretations of this evidence *might* indicate Mars still had *some* water. I know Mars researchers are still debating the amount and locations of Martian water to this day, even including the possibility that Mars has very little water. I think you should mention this uncertainty in every piece you do about water on Mars.

    I note you say “the evidence of *ancient* water on Mars is overwhelming.” I also note you say nothing about the evidence of *present-day* water on Mars. I agree it seems likely that Mars has had *some* water. I think it likely that Mars still does have *some* water, although probably a great deal less then it once had. But, I think it absurdly presumptious to imagine that one can know beyond doubt that “a billion years ago–liquid water was abundant on Mars.” This latter statement is “science” of the sort practiced by Percival Lowell.

    By the way, I apologize for not getting your name right. On my screen it appeared in light brown at the end of your piece. Given that I am visually handicapped–so much so that I can’t use a telescope–I misread an “i” for an “l.” Accusing disabled people of being sloppy can be very ironic sometimes.

  49. Jen

    WOW! How did it go from a delightful discussion filled with “scientific speculation” (which is, to many, the origin of ALL science), to sounding like crotchety old buggars in a know-it-all competition?

    If we had to worry about name calling and accusations of sloppiness, we would never have made the progress thus far in any field. So much of what we rely on today is mere theory, albeit WORKING theory, but theory nonetheless. Hard as we try to nail down science facts, most of them stem from our imaginings, wonderings and speculation. We try it out, if it works, we guess why, if it doesn’t we still guess but try something else. With the explosion of DNA science, we are discovering long held understandings, (that passed for fact until now), are false. Species designations that have stood for as long as they have existed are now being shown to be off by more than the 2% difference between humans and chimps. That doesn’t mean biologists were sloppy, it means with new information comes new interpretations. It’s called advancement.

  50. I want to know about alliens that they are really in the space.
    Is there any other planet inthe universe.that is far far away from earth is it so please reply me .


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