Thumbprints on Mars!

Chronological Encyclopedia of Discoveries in Space cover

After being in print for twenty years, the Chronological Encyclopedia of Discoveries in Space, covering everything that was learned on every single space mission in the 20th century, has finally gone out of print.

I presently have my last four hardback copies available for sale. The book sold new for about $90. To get your own autographed copy of this now rare collector's item, please send a $120 check (which includes shipping) payable to Robert Zimmerman to

Behind The Black, c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652

"Useful to space buffs and generalists, comprehensive but readable, Bob Zimmerman's Encyclopedia belongs front and center on everyone's bookshelf." -- Mike Collins, Apollo 11 astronaut


"The Chronological Encylopedia of Discoveries in Space is no passionless compendium of information. Robert Zimmerman's fact-filled reports, which cover virtually every spacecraft or probe to have ventured into the heavens, relate the scientific and technical adventure of space exploration enthusiastically and with authority." -- American Scientist

Thumbprints terrain on Mars!
Click for full image.

Honestly, don’t ask me. I didn’t come up with the name. I found the image on the right, cropped and reduced to post here, as part of the April image dump from the high resolution camera of Mars Reconnaissance Orbiter. The uncaptioned release dubbed this “Thumbprint Terrain in Northern Mid-Latitudes,” and it is obvious to see why. The cropped image on the right focuses in on the oval white mounds that really do look like some giant child was touching a soft damp muddy surface randomly with his fingers, leaving behind raised fingerprints as the mud stuck to his fingers as he pulled them away.

Each white area seems to have a crater. I suspect these are not impact craters, but possibly mud volcanoes, as each is at the top of a mound. My hypothesis is further strengthened by the location, which is deep within the low northern plains of Mars, a place where some scientists believe an intermittent ocean once existed. These mounds could have easily formed at that ocean’s floor, or thereafter when the land here was drying out.

On the other hand, these could be from impact. Maybe they are scattered ejecta from a larger impact, landing here in a group on a wet muddy surface. The impacts might have concentrated the material around the crater, making it more resistant to erosion, which is why the craters now stand above the floor of the plain.

On the third hand, all these theories could be wrong. Have any of your own?



  • mpthompson

    Hmmm, what do impact craters look like that are formed under a few hundred meters of water? Do they form indistinct impressions such as these?

  • Lee S.

    I doubt it very much…. On mud flats they might… But unless the meteorite is truly massive it wouldn’t…
    The reason almost all impact craters are round, no matter the angle of the impact is because the damage is not caused by the meteorite throwing out ejecta, but by the acctual energy released by the impact… Think a nuclear bomb… If dropped from above or launched in at a low angle on a missile the blast range will still be circular.

    An impact into water of any significant depth would release it’s kinetic energy upon contact with the water, and whilst it might cause a sunami on the surface it could not create such perfectly formed craters.

    I’m thinking mud flats or, like on, mud volcanoes ….

  • Lee s

    ” Like Bob, mud volcanoes” even! ;-)

  • Edward_2

    Mars is a much more interesting place than the Moon.

    There should be 100+ rovers rolling over Mars – exploring every inch of Mars.

    How about robots BUILDING and REPAIRING rovers/robots ON Mars?

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