The sea of dunes surrounding the Martian north pole
Click for full image.
Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on December 5, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a collection of wormlike dunes located in the giant sea of dunes that surrounds the Martian north pole ice cap.
North is to the top. The season when this picture was taken was northern winter. The Sun is barely above the horizon, only 8 degrees high, and shining from the southeast. Because it is winter it is also dust season, making the atmosphere hazy and thus making the light soft. No distinct shadows, except that the sides of the dunes facing away from the Sun are darkly shadowed.
The consistent orientation of the dunes suggests that the prevailing winds blow from the northeast to create the steep-sided alcoves. The wind however might not be the only factor to form these dunes.
The black cross on the center right of the overview map to the right marks the location of these dunes, in the part of Olympia Undae where dune coverage is somewhat intermittent.
At this time in winter these dunes are likely covered with a thin mantle of clear dry ice that fell as snow when winter began. When spring arrives in a few months that mantle will begin to sublimate away, from the bottom up because sunlight shines through the clear dry ice to warm the underlying ground. The pressure of the trapped gas will eventually cause the mantle to crack at weak points, usually at the base of the dunes. The escaping gas will then spew dust onto the mantle, creating dark splotches that will disappear once the mantle is entirely gone.
Some scientists theorize that the coming and going of this mantle could also shape these dunes over time. At this time however the data is insufficient to determine one way or the other.
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
Click for full image.
Cool image time! The photo to the right, rotated, cropped, and reduced to post here, was taken on December 5, 2022 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a collection of wormlike dunes located in the giant sea of dunes that surrounds the Martian north pole ice cap.
North is to the top. The season when this picture was taken was northern winter. The Sun is barely above the horizon, only 8 degrees high, and shining from the southeast. Because it is winter it is also dust season, making the atmosphere hazy and thus making the light soft. No distinct shadows, except that the sides of the dunes facing away from the Sun are darkly shadowed.
The consistent orientation of the dunes suggests that the prevailing winds blow from the northeast to create the steep-sided alcoves. The wind however might not be the only factor to form these dunes.
The black cross on the center right of the overview map to the right marks the location of these dunes, in the part of Olympia Undae where dune coverage is somewhat intermittent.
At this time in winter these dunes are likely covered with a thin mantle of clear dry ice that fell as snow when winter began. When spring arrives in a few months that mantle will begin to sublimate away, from the bottom up because sunlight shines through the clear dry ice to warm the underlying ground. The pressure of the trapped gas will eventually cause the mantle to crack at weak points, usually at the base of the dunes. The escaping gas will then spew dust onto the mantle, creating dark splotches that will disappear once the mantle is entirely gone.
Some scientists theorize that the coming and going of this mantle could also shape these dunes over time. At this time however the data is insufficient to determine one way or the other.
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
I see worm sign.