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Searching for ice in the Martian low latitudes

Low latitude crater with intriguing debris on its floor
Click for full image.

Today’s cool image well illustrates the effort of planetary scientists to map out the range of buried ice on the Martian surface. Taken on December 13, 2020 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and rotated, cropped, and reduced to post here, it shows a 3.5-mile-wide crater located in the southern cratered highlands, but for those cratered highlands at the very high northern latitude of 24 degrees.

The black streaks on the crater’s interior slopes are probably slope streaks, but these are not the subject of this article. Instead, it is the material that covers the crater’s floor. These features resemble the glacial fill material that scientists have found widespread in the latitude bands between 30 to 60 degrees latitude. However, this crater is farther south, where such ice would not be stable and should have sublimated away.

Could there still be ice here? I emailed the scientist who requested the photo, Colin Dundas of the U.S. Geological Survey’s Astrogeology Science Center in Arizona, and asked him what I was looking at. His answer:

This is an interesting image. It does indeed have morphology similar to debris-covered glaciers elsewhere on Mars. Some work by David Shean (published in Geophysical Research Letters in 2010) shows even lower-latitude crater-filling material resembling this.

Ice at these latitudes would be unstable at present, but it could be slowly sublimating if there was an episode of (geologically) recent deposition–Shean’s paper suggested that this could have occurred during recent high-obliquity episodes. Alternatively, it could be relict debris that was shaped by sublimation of buried ice that is now completely gone.

Based on the orbital data alone they as yet cannot make a certain determination. If however this is buried ice or even simply debris that marks the past presence of ice, it provides evidence of the earlier eons when ice and water were more ubiquitous on Mars, even in equatorial regions.

Both Perseverance at 18 degrees north latitude in Jezero Crater and China’s rover at 24 degrees north latitude in the northern lowland plains of Utopia Planitia will be doing the same searching, looking to see if water or ice still exists in these equatorial regions.

Finding out yay or nay will do much to clarify the geology of Mars, both past and present.

Pioneer cover

From the press release: From the moment he is handed a possibility of making the first alien contact, Saunders Maxwell decides he will do it, even if doing so takes him through hell and back.

Unfortunately, that is exactly where that journey takes him.

The vision that Zimmerman paints of vibrant human colonies on the Moon, Mars, the asteroids, and beyond, indomitably fighting the harsh lifeless environment of space to build new societies, captures perfectly the emerging space race we see today.

He also captures in Pioneer the heart of the human spirit, willing to push forward no matter the odds, no matter the cost. It is that spirit that will make the exploration of the heavens possible, forever, into the never-ending future.

Available everywhere for $3.99 (before discount) at amazon, Barnes & Noble, all ebook vendors, or direct from the ebook publisher, ebookit. And if you buy it from ebookit you don't support the big tech companies and I get a bigger cut much sooner.


  • John K. Strickland

    Locating substantial amounts of underground water ice closer to the Mars equator than the current band of about 38 to 60 degrees N. Latitude. is crucial, and not just for geological and climatological history. Certain well known people are looking for an initial construction base site that would lead to a Mars settlement. The closer the site is to the equator, the warmer it is, the more sunlight you get, and the less delta-V needed to land there. Water ice is crucial to most Mars plans now since without it, you cannot produce rocket fuel and take off again. LOX can be made from CO2, but to make LH2 and/or methane, you do need a source of hydrogen. Water ice is it. NASA’s dedicated water ice detection mission could be launched in 2026, the same year that the first human mission could be sent to Mars by SpaceX. Practically, you cannot land crew until you can prove there is ice at the location. Too bad that ice mission could not be launched in 2024, but putting a mission together in just 3 years would be extremely difficult if not impossible. I wonder how this timing problem will be solved.

  • John K. Strickland. First, ice has been located with great confidence at latitudes as low as 32 degrees.

    Second, SpaceX’s candidate landing site for Starship is in a location where a lot of ice is now thought to exist. See this post on BtB: SpaceX completes 1st round of Starship’s Mars landing site images. The latitude is around 39 degrees north, but it is in the northern lowland plains, which makes sense for a first landing. Ice is thought to be so plentiful here and so close to the surface that one scientist has noted in a presentation that you could hit it by simply sticking a shovel in the ground.

  • Water vapor is present in the martian atmosphere in a proportion of 0.210%. Couldn’t hydrogen be obtained from that?

  • John K. Strickland

    I just want the SpaceX operation to be able to land as close to the Mars equator as possible as long as there is ground truth proving that the ground ice is there. The 40 degree north set of locations is in a nice flat area, but it is almost half-way to the pole, and the local mineral resources (other than water) may not be well known. You cannot build pressurized habitats out of ice. Would you want to put a base on Antarctica with at least a mile of ice between you and bedrock? A base at the edge of a ground ice area might be a better location. The targeting accuracy and obstacle avoidance capability of the Perseverance Rover system has now shown our ability to land safely in areas that have some very rough terrain.

    I suspect that trying to extract water vapor from the Mars atmosphere, while physically possible, is grossly impractical. The air over the Atacama Desert is probably wetter than the Mars atmosphere. It is impractical due to the massive amount of equipment and energy that would be required. How much energy would be needed to extract just one kilogram of water, to say nothing about the thousand of tons that will be needed to support a development base, allowing the supply Starship vehicles to return to Earth for more loads. Digging the ice up, melting and filtering it is vastly easier.

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