Click for original image.
Cool image time! The photo to the right, cropped, reduced, and sharpened to post here, was taken on September 26, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The science team labeled this “Possible Pit,” but other than a small dark stain on the rim of a crater north of the section cropped to the right, I could find nothing that even closely resembled a pit. More likely the scientists were referring to the large circular depression in the top center of this picture. It does not at first glance look like a crater, as it has no obvious rim. In fact, almost none of the circular depressions in this image look like craters, as almost none have uplifted rims.
However, it is not clear what caused these dust-filled fractures as well as the image’s many circular depressions. The location, as indicated by the overview map below, does not really help.
The small red dot, south of Cerberus Fossae and inside the Medusae Fossae Formation, Mars’s biggest deposit of volcanic ash, marks the location of these cracks. Though this is very close to one of the large quakes detected by InSight, these cracks are much much older.
Because this is near the equator, there is no near surface ice here. This is very dry terrain. Being inside Medusae Fossae explains the amount of ash filling the fissures and pits. In fact, it could be we are seeing chaos terrain whose intersecting canyons are almost entirely filled with that ash.
Or not. Maybe the ash is so thick here that impacts don’t form rims, but disappear into the ash like a hot pebble falling into ice.
This is also in a region of many vast flood lava plains. The surface here is likely lava, but why it has these cracks and fissures is beyond my status as an amateur geologist to explain.
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