New gravity map of Mars released
Click for original image.
Using both seismological data compiled over four years by the InSight Mars lander as well tiny changes in the orbits of Martian satellites, scientists have now created a global gravity map of the red planet, indicating the regions below the surface that are either low or high density.
That map is above, annotated by me to indicate some of Mars’ major surface features.
The density map shows that the northern polar features are approximately 300-400 kg/m3 denser than their surroundings. However, the study also revealed new insights into the structures underlying the huge volcanic region of Tharsis Rise, which includes the colossal volcano, Olympus Mons.
Although volcanoes are very dense, the Tharsis area is much higher than the average surface of Mars, and is ringed by a region of comparatively weak gravity. This gravity anomaly is hard to explain by looking at differences in the martian crust and upper mantle alone. The study by Dr Root and his team suggests that a light mass around 1750 kilometres across and at a depth of 1100 kilometres is giving the entire Tharsis region a boost upwards. This could be explained by huge plume of lava, deep within the martian interior, travelling up towards the surface.
I once again note that the largest impact basin on Mars, Hellas Basin, sits almost exactly on the planet’s far side from Tharsis, and appears to have a light density. This contrast once again makes me wonder if the origin of that impact and the Tharsis Bulge are linked.
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 print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. 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 original image.
Using both seismological data compiled over four years by the InSight Mars lander as well tiny changes in the orbits of Martian satellites, scientists have now created a global gravity map of the red planet, indicating the regions below the surface that are either low or high density.
That map is above, annotated by me to indicate some of Mars’ major surface features.
The density map shows that the northern polar features are approximately 300-400 kg/m3 denser than their surroundings. However, the study also revealed new insights into the structures underlying the huge volcanic region of Tharsis Rise, which includes the colossal volcano, Olympus Mons.
Although volcanoes are very dense, the Tharsis area is much higher than the average surface of Mars, and is ringed by a region of comparatively weak gravity. This gravity anomaly is hard to explain by looking at differences in the martian crust and upper mantle alone. The study by Dr Root and his team suggests that a light mass around 1750 kilometres across and at a depth of 1100 kilometres is giving the entire Tharsis region a boost upwards. This could be explained by huge plume of lava, deep within the martian interior, travelling up towards the surface.
I once again note that the largest impact basin on Mars, Hellas Basin, sits almost exactly on the planet’s far side from Tharsis, and appears to have a light density. This contrast once again makes me wonder if the origin of that impact and the Tharsis Bulge are linked.
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 print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. 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
What strikes me is how starkly the Valles Marinaris canyon is defined. Obviously there is less mass in this region as it is a void, but I would not have anticipated that a gravity map would render it so clearly.
Tharsis the antipode of the Hellas crater?
Robert wrote: “I once again note that the largest impact basin on Mars, Hellas Basin, sits almost exactly on the planet’s far side from Tharsis, and appears to have a light density. This contrast once again makes me wonder if the origin of that impact and the Tharsis Bulge are linked.”
Sort of like if a large meteor hit at Hellas Basin and the shock wave damaged the crust on the other side like a bullet hitting a watermelon?
https://www.youtube.com/watch?v=bP2H_pP6uhg (2 minutes)
The Caloris Basin on Mercury also may have caused the chaotic terrain on the opposite side of the planet
Something like this has also been proposed for earth—in that the dinosaur-killer Chicxulub impact on what’s now the coast of the Yucatan peninsula in Mexico is located basically on precisely the opposite side of earth from where the series of enormous “Deccan Traps” volcanic eruptions was then ongoing—which hadn’t yet resulted in any extinctions—but which thereupon became much more severe, contributing to the oncoming extinction catastrophe (3/4 of all species, land and sea, became extinct following that impact). The idea is that seismic waves from the impact propagated through the earth, focussing at the impact site’s antipode, making it much worse.
But, lately, I believe, this theory has been somewhat disfavored, however I’m not sure why.
Michael McNeil: I’ve written about this subject in the past. My understanding is that there is great skepticism among paleontologists about the Chicxulub impact as the primary cause of the extinction event. Their research sees the Deccan Traps as a major factor as well — maybe the most important — noting that this major volcanic event had been going on prior to the impact. There is evidence in the bone records that it was causing many extinctions before the impact.
Other paleontogical data also suggests the impact did not wipe out the dinosaurs, that the extinction event continued for a great deal of time thereafter. As you note, the eruption of the Deccan Traps continued for many decades, resulting in more extinctions.
That it might have directly become more severe because of that impact on the other side of the world is a new idea to me, and quite interesting.
Check out the Nadir crater–dates to roughly 66 million years.
It probably took a one-two (three?) punch to kill the dinosaurs off.
Jurassic to Triassic was just a “pause” button—not “reset.”
Jeff–
Very interesting subject.
I rather think Chicxulub by itself was a necessary but not sufficient cause.
Should a wobble in Mars’ rotation and then it’s orbit be detectable and calculable due to this gravity distribution?
Does this map of the surface reflect density changes through the planet or only near the surface? On earth I have read that gravity differences can be measured near mountains. Is this considered surface or fully through the earth? Or, is that not known?
Chris-
I’m not the one to explain this, but (in part);
“Separated objects attract and are attracted as if all their mass were concentrated at their centers.”
And, this follows the inverse square law.
Hi Wayne
Thanks
I see your point – the axis of rotation should “settle” about a line -axis – that is the sum of the masses involved. Although, I’m not sure what would act to settle this motion – liquid core and atmosphere and water on earth (others?) If the gravity distribution is due to the impacts then I suspect setting is not complete. The planet may still be ringing due to the impacts as the moon supposedly is from an impact in the 1400’s(?) but I wonder about wobble.
The planet should be wobbling due to gravitational tugs from other planets, moons, etc. This/ these component(s) should be able to be separated.
Interesting.
Chris–
Maybe one of our more hard-science people would weigh in.