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Scientists: Liquid surface water might have existed on Mars as recently as 2.3 billion years ago

Map showing locations of salt deposits
Click for full image.

Using orbital data from Mars Reconnaissance Orbiter (MRO), scientists have found salt deposits on Mars where nearby crater counts suggest that the salt water that once held these deposits could have evaporated away as recently as 2.3 billion years ago.

Using [MRO’s] cameras to create digital elevation maps, Leask and Ehlmann found that many of the salts were in depressions – once home to shallow ponds – on gently sloping volcanic plains. The scientists also found winding, dry channels nearby – former streams that once fed surface runoff (from the occasional melting of ice or permafrost) into these ponds. Crater counting and evidence of salts on top of volcanic terrain allowed them to date the deposits.

Past data has suggested that if liquid surface water had existed on Mars, it was gone by three billion years ago.

You can read the scientists’ research paper here.. The maps to the right, figure two from the paper, shows the locations of discovered salt deposits, almost all of which are in the Martian southern cratered highlands of Mars.

Is there uncertainty in these results? My regular readers know that the answer is of course yes. The biggest problem for these Mars researchers is that, despite the surface evidence that liquid water should have once flowed on the surface of Mars, no scientist has yet come up with a satisfactory model of Mars’ past climate that would have made that possible. The planet was either too cold or had too thin an atmosphere, based on other data. And getting it warmer or with a thicker atmosphere involves inventing any number of scenarios that are all questionable, based on what is presently known.

There is also the increasing evidence that glaciers of ice, not water, might have carved those winding, dry channels. If so, many of the assumptions that liquid water existed might simply be wrong, or incomplete. The scientists who wrote this report recognize this importance of ice on Mars, and note in their abstract that

…we think that the water source came from surface runoff, rather than deep groundwater welling up to the surface. The small amounts of water required are most likely from occasional melting of ice.

As always, more data is needed, with the most useful data that will clarify these conclusions being that gathered by future colonists on the surface of Mars itself.


Conscious Choice cover

Now available in hardback and paperback as well as ebook!


From the press release: In this ground-breaking new history of early America, historian Robert Zimmerman not only exposes the lie behind The New York Times 1619 Project that falsely claims slavery is central to the history of the United States, he also provides profound lessons about the nature of human societies, lessons important for Americans today as well as for all future settlers on Mars and elsewhere in space.

Conscious Choice: The origins of slavery in America and why it matters today and for our future in outer space, is a riveting page-turning story that documents how slavery slowly became pervasive in the southern British colonies of North America, colonies founded by a people and culture that not only did not allow slavery but in every way were hostile to the practice.  
Conscious Choice does more however. In telling the tragic history of the Virginia colony and the rise of slavery there, Zimmerman lays out the proper path for creating healthy societies in places like the Moon and Mars.


“Zimmerman’s ground-breaking history provides every future generation the basic framework for establishing new societies on other worlds. We would be wise to heed what he says.” —Robert Zubrin, founder of founder of the Mars Society.


All editions are available at Amazon, Barnes & Noble, and all book vendors, with the ebook priced at $5.99 before discount. The ebook can also be purchased direct from my ebook publisher, ebookit, in which case you don't support the big tech companies and I get a bigger cut much sooner.


Autographed printed copies are also available at discount directly from me (hardback $24.95; paperback $14.95; Shipping cost for either: $5.00). Just email me at zimmerman @ nasw dot org.


  • Questioner

    Oh, just 2.3 billion years ago, so practically yesterday! :-)

  • Questioner

    Hello Mr Zimmerman,

    I share your enthusiasm for the geological sensations of Mars. He’s a beautiful corpse. A corpse whose life was very brief at best, dying a whopping 2.3 billion years ago. A corpse that I believe only gods can revive.

    How about turning your attention to the moon Titan as well? Compared to Mars, it has at least an atmosphere worth mentioning. But well, the temperatures there, -179 degrees Celsius, are not exactly heartwarming. There, the gravity of 1/7 g is even lower than on our moon.

    How do you mean? Where do I die faster without a space suit? On Mars or on Titan?

    Best regards, Questioner

  • Questioner: My reporting seems overall focused on Mars not because that is my focus, but that is where the research probes are. If we had an orbiter or lander or rover at Titan, you can bet I’d report on it quite regularly.

  • pzatchok

    I still think there is a lot of water on Mars.

    Its just really deep. And I mean really really deep.

    What keeps water on the surface of the Earth? Internal heat.

    Mars doesn’t have enough deep internal heat to boil a cup of water let alone push an oceans worth up.
    When it was fresh and new i bet it was warm enough for liquid water. But as it cooled it sank into the surface.

    All the water on Mars is actually as deep as it can flow towards the center of the planet. Its had billions of years to move down.

    Or its just slowly disappearing permafrost.

  • Questioner

    Mr Z:

    Well, the existence of salt lakes on Mars has been proven, which existed until 2.3 billion years ago.

    Is it true that there is no evidence of the existence of an ocean surrounding the planet? Or how is the situation there?

  • Questioner


    Are you talking about a water table? Shouldn’t there be evidence of that? There are places on earth where groundwater rises to the surface. In the case of Mars, it then turns to ice. But maybe this will then show a pattern by which the groundwater leakage can be recognized.

  • Questioner and Pzatchok: Please see this post from February 2021:

    The Icy Surface of Mars

    Or this post from 2020:

    The salty liquid water on Mars

    Or this post from 2019:

    A new map of the water ice on Mars

    Or this post from 2019:

    Further explorations at candidate Starship Mars landing site

    Or simply do a search on BtB for “Mars” and “glaciers.” You will find endless stories documenting the presence of water ice very close to the surface on Mars from 30 degrees latitude poleward.

    Questioner is pretty new here, but I am surprised pzatchok seems so unaware of this data, considering he has been a regular commenter here for years.

  • pzatchok

    I am aware of all those.

    None of those mean the majority of the water. And my guess is that oceans worth are locked super deep close to the core.

    Whats on the surface is actually less than on the surface of the Earths driest desert.

    ‘My guess is that the most economical way of getting water from Mars would be atmospheric extractors. Yes sort of like Star Wars.
    No need to mine huge mega tones of dirt just to extract a few gallons of water.

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