New research confirms the steady decline of Martian ice with each glacial cycle
Using orbital data from Mars Reconnaissance Orbiter (MRO) of glaciers inside mid-latitude craters, scientists have concluded that there was a steady decline in the growth of those glaciers with each new glacial cycle.
They focused on craters with indicative signs of glaciation, such as ridges, moraines (piles of debris left behind by glaciers), and brain terrain (a pitted, maze-like surface formed by ice-rich landforms). By comparing the shapes and orientations of these features with climate models, they found that ice consistently clustered in the colder, shadowed southwestern walls of craters. This trend was consistent across various glacial periods, ranging from approximately 640 million to 98 million years ago.
The results show that Mars didn’t just freeze once—it went through a series of ice ages driven by shifts in its axial tilt, also known as obliquity. Unlike Earth, Mars’ tilt can swing dramatically over millions of years, redistributing sunlight and triggering cycles of ice build-up and melting. These changes shaped where water ice could survive on the planet’s surface. Over time, however, each cycle stored less ice, pointing to a gradual planetary drying. [emphasis mine]
You can read the paper here [pdf]. This result is not new. Based on the orbital data scientists have theorized now for almost a decade that as Mars’ rotational tilt (its obliquity) swings from 11 to 60 degrees, it produces extreme climate cycles on the planet. Those swings are shown on the graph to the right, taken from this 1993 paper [pdf]. When the obliquity is low, the mid-latitudes are warm and the glaciers there shrink, with the snow falling at the poles. When obliquity is high, the poles are warmer and its ice sublimates away to fall as snow in the mid-latitudes, thus causing those glaciers to grow instead.
The orbital data has consistently shown that with each new cycle, the glaciers grew less, suggesting that less global water was available on the planet. This new study further confirms these conclusions.
One last point: Though the amount of water ice on Mars has declined, we mustn’t think the red planet now has none. The orbital data shows that there is a lot of near surface ice on Mars, covering the planet from 30 degrees latitude poleward. As I’ve noted numerous times, Mars is a desert like Antarctica.
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
Using orbital data from Mars Reconnaissance Orbiter (MRO) of glaciers inside mid-latitude craters, scientists have concluded that there was a steady decline in the growth of those glaciers with each new glacial cycle.
They focused on craters with indicative signs of glaciation, such as ridges, moraines (piles of debris left behind by glaciers), and brain terrain (a pitted, maze-like surface formed by ice-rich landforms). By comparing the shapes and orientations of these features with climate models, they found that ice consistently clustered in the colder, shadowed southwestern walls of craters. This trend was consistent across various glacial periods, ranging from approximately 640 million to 98 million years ago.
The results show that Mars didn’t just freeze once—it went through a series of ice ages driven by shifts in its axial tilt, also known as obliquity. Unlike Earth, Mars’ tilt can swing dramatically over millions of years, redistributing sunlight and triggering cycles of ice build-up and melting. These changes shaped where water ice could survive on the planet’s surface. Over time, however, each cycle stored less ice, pointing to a gradual planetary drying. [emphasis mine]
You can read the paper here [pdf]. This result is not new. Based on the orbital data scientists have theorized now for almost a decade that as Mars’ rotational tilt (its obliquity) swings from 11 to 60 degrees, it produces extreme climate cycles on the planet. Those swings are shown on the graph to the right, taken from this 1993 paper [pdf]. When the obliquity is low, the mid-latitudes are warm and the glaciers there shrink, with the snow falling at the poles. When obliquity is high, the poles are warmer and its ice sublimates away to fall as snow in the mid-latitudes, thus causing those glaciers to grow instead.
The orbital data has consistently shown that with each new cycle, the glaciers grew less, suggesting that less global water was available on the planet. This new study further confirms these conclusions.
One last point: Though the amount of water ice on Mars has declined, we mustn’t think the red planet now has none. The orbital data shows that there is a lot of near surface ice on Mars, covering the planet from 30 degrees latitude poleward. As I’ve noted numerous times, Mars is a desert like Antarctica.
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
Global warming!
And don’t you deny it.
To get more water to Mars, it looks like humans will have to shift icy comets, or parts of Europa/Enceladus to orbit the Red Planet. Placed in orbit first, and massive enough to shrink the obliquity range to 20 to 30 degrees, to stabilize the condensation/sublimation cycle, then shave off a few hundred-million tons annually to fall as rain.
The first case of bottled Europan water, slightly carbonated, should sell for enough to cover the U.S. debt in several thousand years.
Don C: You need to reread my last paragraph in this post. Mars still has gobs of water. There will be many other much more important tasks for the first, second, and even hundredth settlers to tackle first.
Martian’s must swear off their big SUV’s and pickup trucks to stop Global Warming. That is the ONLY conclusion possible.
I can show you the Martian Koradteebar* chart that PROVES it.
Believe the SCIENCE!!
* Barsoomian for Hockey Stick
The first thing to do is to get an artificial magnetosphere around Mars. The Sun will steadily blow away whatever Martian volatiles we unearth. Comet wrangling might help.
I just wish I could dump most of Venus’ atmosphere on Mars in one go. Let the Sun blow that away.
What happens to Phobos and Deimos when Mars’ obliquity changes?
Jeff Wright: Charlie Martin estimates how long that will take here: https://space2025.substack.com/p/will-a-terraformed-mars-leak
The present rate of solar-wind erosion of the atmosphere on Mars is a mere 1-2 kg/second, a rate which can easily be much more than made up for by human activity. Mars’ loss of atmosphere has occurred over billions of years.
The physics of the planet remain constant no matter how much fantasy you throw at it.
Mars is 1/2 the size of the earth with 1/3 of the gravity. Even though the atmosphere pressure at .007 mbar Is near vacuum, the atmosphere of mars extends almost twice as far into space as earths atmosphere does. It took billions of years losing its former thicker atmosphere to come to this balance where it is nearly stable.
There is enough CO2 ice on the north and South Pole, should you melt it into a gas, to more than double the thickness of the atmosphere. But this would also triple the distance into space the atmosphere would extend. Gravity becomes weaker at the inverse square of the distance meaning a lot of the atmosphere will simply drift off like a comets tail behind Mars.
The problem of terraforming mars has always been the lack of mass… colliding large amount of astroids or small moons from outer Jupiter and Saturn into Mars to increase its mass is not feasible. And would just serve to destroy the planet making it unapproachable for hundreds of years.
Comets of water ice could be set into an decaying elliptical orbit to add mass by melting in the upper atmosphere a little bit at a time without any planetary destruction if a sufficient supply could be found.
A alternative is to substitute the atmosphere with a heavier molecule that will provide atmospheric pressure and heat. A heavier molecule like chlorofluorocarbon, or other complex molecules that resist breaking down under UV radiation.
At twice the distance from the sun, photosynthesis is unlikely to be productive, so living on the surface is not realistic. With a thicker artificial atmosphere you won’t need to have the bulky space suits, just a way to breathe, and the heat generated by the air pressure will provide enough warmth to be manageable. Liquid H402 (“water”….there’s no such thing as H2O outside a laboratory) Will be a problem, being very buoyant as it is here on earth, and will float above heavier air molecules (like oil on top of water) into outer space just like CO2 and nitrogen and oxygen.
Every solution has its unintended consequences.
I see no long-term alternative to human habitation outside of pressurized structures on the surface and pressurized containers under ground to prevent poisonous gases leaking into the habitable caves and tunnels. (robotics is the future of most habitable construction and maintenance).
Even living in the ice caps themselves, where the poisonous gases of CO2 can be managed, will have other challenges to overcome… It would at least solve the problem of plentiful water, nitrogen, and a mostly dust free environment from the resources of tunneling into the ice. (The cold is an issue requiring a large energy source no matter where you live on Mars)
As for Venus, better to focus on “Bio Geo engineering” of a buoyant carbon dioxide eating plankton that is suspended in the upper atmosphere to “reduce” (eat) the atmosphere of Venus into Methane, water and oxygen to eventually infect and survive on the surface making calcium carbonate to condense the current atmosphere onto the surface as a solid. (That’s what happened to earth that formed its lime stone mountains and fossil fuels)
The same could be done for Saturn and possibly Neptune and Uranus as well. Saturn would be reduced to a Waterworld with only 10% more gravity than earth… it would probably still be too hot, but the rings surrounding the huge water planet would be beautiful! All that’s required is the introduction of life without a natural enemy and it will reproduce until it consumes all of the CO2 in the atmosphere. Eventually it will choke on its own waste byproduct (Poisonous oxygen) and the reaction will slow to a crawl. At this point the planet is ready for higher life forms.