Scroll down to read this post.


My July fund-raising campaign, celebrating the 13th anniversary of the start of this website, has now ended. This was the second most successful monthly fund-raising campaign ever. Thank you again to everyone who has who donated or subscribed. It is difficult to explain what your support means to me.


You can still donate or subscribe to support my work if you wish, either by giving a one-time contribution or a regular subscription. There are four ways of doing so:


1. Zelle: This is the only internet method that charges no fees. All you have to do is use the Zelle link at your internet bank and give my name and email address (zimmerman at nasw dot org). What you donate is what I get.


2. Patreon: Go to my website there and pick one of five monthly subscription amounts, or by making a one-time donation.

3. A Paypal Donation:

4. A Paypal subscription:

5. Donate by check, payable to Robert Zimmerman and mailed to
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652

Zhurong data suggests a more watery Martian environment more recently that previously thought

The Martian obliquity over the past 80 million years
The graph comes from this paper [pdf], and shows the shift of Mars’
rotational tilt, or obliquity, for the past 80 million years.

Scientists analyzing data obtained by China’s Zhurong rover during its first four months on Mars have concluded that the Martian atmosphere in the northern lowland plains of Utopia Planitia has been more active hydrologically much more recently than previously believed.

You can read the paper here. From its conclusions:

Unlike the weak and friable thin veneer or crusty clods at previous landing sites for Mars Exploration Rovers and InSight lander, these rocks are more akin to the fractured duricrust observed at the Viking Lander 1 site. The thin and brittle layer of duricrust has been proposed to form by salt cementation via water vapor diffusion from the atmosphere. In contrast, duricrusts at Zhurong landing site appear to be more resistant to erosion, forming cliffs perched through loose soils in the surroundings, which require a substantial amount of liquid water rather than water vapor.

…The morphology and spatial extent of platy and bright-toned rocks investigated by the Zhurong rover argue for in situ formation and degradation of these rocks in the Amazonian-aged geological unit in southern Utopia Planitia. These observations suggest that aqueous activities may have persisted much longer than previously thought. Periodical climate cycles on Mars driven by obliquity oscillations are expected to result in a latitude-dependent distribution of ground ice over geologic history. Higher obliquities (>45°) could mobilize polar ice and form glaciers and water ice sheets at midlatitudes and stabilize ground ice at Zhurong landing site for extended periods of tens of thousand years when the obliquity exceeded 29° to 33°. The hydrated minerals and widespread salt cementations imply the presence of briny liquid water in the subsurface, which may have been generated by melting the ground ice during temporary climate perturbations (e.g., volcanism and impacts).

Obliquity refers to the planet’s rotational tilt, which fluctuates from 11 to 65 degrees, and is presently tilted at 25 degrees, only slightly different than Earth’s 23 degree tilt. Since Mars’ obliquity has exceed 29 degrees numerous times in the past 80 million years, as shown by the graph above, that means it was possible that this now dry equatorial region on Mars had seen plenty of surface water or ice as recently as a few million years ago, far more recently than the three billion years previously estimated.

For liquid water to have existed on the surface is still difficult, because Mars’ atmosphere would have been too thin and cold. However, if ice sheets had existed here, there is the possibility that the ice would have become liquid at the sheet’s base, and interacted with the ground in some manner to produce the duricrust now observed.

Genesis cover

On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.

The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.

"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News

One comment

Readers: the rules for commenting!


No registration is required. I welcome all opinions, even those that strongly criticize my commentary.


However, name-calling and obscenities will not be tolerated. First time offenders who are new to the site will be warned. Second time offenders or first time offenders who have been here awhile will be suspended for a week. After that, I will ban you. Period.


Note also that first time commenters as well as any comment with more than one link will be placed in moderation for my approval. Be patient, I will get to it.

Leave a Reply

Your email address will not be published. Required fields are marked *