Leaving Earth cover

In 2019 I obtained from my former publisher the last 30 copies of the now out-of-print hardback of Leaving Earth. I sold about half of these, and with only a handful left in stock I have raised the price. To get your own autographed copy of this rare collector's item please send a $75 check (includes $5 shipping) payable to Robert Zimmerman to

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

I will likely raise the price again when only ten books are left, so buy them now at this price while you still can!

Also available as an inexpensive ebook!

Leaving Earth: Space Stations, Rival Superpowers, and the Quest for Interplanetary Travel, can be purchased as an ebook everywhere for only $3.99 (before discount) at amazon, Barnes & Noble, all ebook vendors, or direct from my ebook publisher, ebookit.


Winner of the 2003 Eugene M. Emme Award of the American Astronautical Society.

"Leaving Earth is one of the best and certainly the most comprehensive summary of our drive into space that I have ever read. It will be invaluable to future scholars because it will tell them how the next chapter of human history opened." -- Arthur C. Clarke

Partly engulfed Martian craters

An engulfed crater on Mars
Click for full image.

Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken by the high resolution camera on Mars Reconnaissance Orbiter (MRO) on October 31, 2020. It shows a crater that appears buried in a sea of material so that pretty much the only thing visible is top of its rim.

The full image shows a second larger crater to the northwest that looks the same. In both cases the material fills the craters also fills the surrounding terrain.

Yet, both craters appear to be surrounded by a faint skirt of uplifted material.

What caused this situation?

Overview map

The overview map to the right gives a clue. The crater, the black rectangle, is on the outermost slopes of the giant shield volcano Alba Mons. Rather than grow upward significantly, this volcano, which is relatively low for its width, spread outward over a vast region. Even though the above crater is about 600 miles from the volcano’s caldera, it is still within its vast shield.

Also, if you look closely at this crater as well as the larger one in the full image, you will see that both have breaks in their rims in the southeast and northwest quadrants, exactly in line with the direction of flow down from the volcano.

So is the material that surrounds and fills this crater lava from Alba Mons? Probably, but with a major caveat. The crater is located at 46 degrees north latitude, well within the mid-latitude bands where scientists have found lots of evidence of glacial features. Furthermore, the Starship candidate landing zone in Arcadia Planitia is only slightly off the west edge of this overview map, about 900 miles away, where scientists have found evidence of water ice very close to the surface almost everywhere they look.

Thus, we might also be looking at buried ice features here, likely sitting on top of the lava flows that are much older.

As for the skirts surrounding each crater, I suspect we are seeing a reflection of the underground ejecta blanket from the impacts, which likely hit ground with a lot of water ice, and thus produced a splattered look like the crater posted here. Later, lava covered everything, leaving only a hint of that splat.

Then again, none of my hypotheses above might be right. It is also possible that the craters could have been volcanic vents, and the lava came from within them. That would explain the skirts. I think this less likely, but what do I know?

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.

One comment

  • janyuary

    “I think this less likely, but what do I know?”
    Well, I know one thing: when I see UFO enthusiasts showing photographic “proof” of other-planetary structures that look a lot like man-(or alien)-made, I’ll know what the bigger context probably looks like and why it’s omitted! {^)

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