Mars atmosphere well protected from the solar wind

December 8, 2017, Swedish Institute of Space Physics
Charged particles from the sun (the solar wind) form an induced magnetosphere round Mars, which unlike the sun does not have its own intrinsic magnetic field. Credit: Anastasia Grigoryeva

Despite the absence of a global Earth-like magnetic dipole, the Martian atmosphere is well protected from the effects of the solar wind on ion escape from the planet. New research shows this using measurements from the Swedish particle instrument ASPERA-3 on the Mars Express spacecraft. The results have recently been presented in a doctoral thesis by Robin Ramstad, Swedish Institute of Space Physics and Umeå University, Sweden.

Present-day Mars is a cold and dry planet with less than 1 percent of Earth's atmospheric pressure at the surface. However, many geological features indicate the planet had an active hydrological cycle about 3 to 4 billion years ago. An active hydrological cycle would have required a warmer climate in the planet's early history and therefore a thicker atmosphere, one capable of creating a strong greenhouse effect.

A common hypothesis maintains that the solar wind over time has eroded the early Martian atmosphere, causing the greenhouse effect, and thus the hydrological cycle, to collapse. Unlike Earth, Mars has no global magnetic dipole, but the solar wind instead induces currents in the ionized upper atmosphere (the ionosphere), creating an induced magnetosphere.

"It has long been thought that this induced magnetosphere is insufficient to protect the Martian atmosphere," says Robin Ramstad. "However, our measurements show something different."

The Swedish-led ion mass analyser on Mars Express has been measuring the ion escape from Mars since 2004. In his research, Robin Ramstad has combined and compared measurements of the ion escape under varying solar wind conditions and levels of ionizing solar radiation, so-called extreme ultraviolet (EUV) radiation. The results show that the solar wind has a comparatively small effect on the ion escape rate, which instead mainly depends on the EUV radiation. This has a large effect on estimations of the total amount of atmosphere that has escaped to space.

"Despite stronger solar wind and EUV-radiation levels under the early Sun, ion escape can not explain more than 0.006 bar of atmospheric pressure lost over the course of 3.9 billion years," says Robin Ramstad. "Even our upper estimate, 0.01 bar, is an insignificant amount in comparison to the required to maintain a sufficiently strong greenhouse effect, about 1 bar or more according to climate models."

The results presented in the thesis show that a stronger solar mainly accelerates particles already escaping the planet's gravity, but does not increase the ion escape rate. Contrary to previous assumptions, the induced magnetosphere is also shown to protect the bulk of the Martian ionosphere from energy transfer.

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dogbert
3 / 5 (3) Dec 09, 2017
Very interesting.

"Despite stronger solar wind and EUV-radiation levels under the early Sun, ion escape can not explain more than 0.006 bar of atmospheric pressure lost over the course of 3.9 billion years," says Robin Ramstad. "Even our upper estimate, 0.01 bar, is an insignificant amount in comparison to the atmosphere required to maintain a sufficiently strong greenhouse effect, about 1 bar or more according to climate models."


If the solar wind did not strip Mars' atmosphere, then we are left with the question of how Mars lost its early atmosphere.

There is evidence that Mars collided with a very large mass at in its past. Could such a collision have stripped the atmosphere?
Solon
1.2 / 5 (9) Dec 09, 2017
"If the solar wind did not strip Mars' atmosphere, then we are left with the question of how Mars lost its early atmosphere."

Maybe it never had an early atmosphere

"However, many geological features indicate the planet had an active hydrological cycle about 3 to 4 billion years ago."

Assumption again. The geological features may well have been from electrical/plasma causes, and much more recently than is believed. Mainstream of course can not ever admit to one incidence of electrical/plasma surface modification on even one planet or moon as it would negate all presently held beliefs.

jonesdave
3.8 / 5 (11) Dec 09, 2017
Assumption again. The geological features may well have been from electrical/plasma causes, and much more recently than is believed.


Complete nonsense. Please show the theory behind this. Lol - it'll be Velikovsky, as usual!. Nothing to do with science, therefore. Which is why you won't see any serious scientist promoting such idiotic woo.
jonesdave
1.8 / 5 (6) Dec 09, 2017
Very interesting.

If the solar wind did not strip Mars' atmosphere, then we are left with the question of how Mars lost its early atmosphere.

There is evidence that Mars collided with a very large mass at in its past. Could such a collision have stripped the atmosphere?


Well, here is my take on it - after formation, there was a lot of heat around to drive volcanism. This released large amounts of GH gases (i.e. water & CO2) to the atmosphere. As there was water vapour around, then one assumes there was rain to wash the CO2 out of the atmosphere, as on Earth. Unlike Earth, there was no plate tectonics to recycle that carbon. However, as long as it was replenished from volcanism, it would stay warm enough. Once the heat dissipated, and volcanism died out, then the carbon was all sequestered in rocks, and the water was frozen out below surface mainly.
So, if this thesis is correct, then the bulk of the ancient martian atmosphere must still be there, albeit in solid form.
rrwillsj
3.8 / 5 (5) Dec 09, 2017
jd, I agree with your supposition until your final conclusion that water ices are still there. Beneath the surface, protected by the sands covering it.

Here on Earth, high deserts are notorious for dryer than dry. Even on this water world Earth, there is constant evaporation from the ground layer.

On Mars? Over billions of years of near vacuum? Desiccation does not even begin to describe how Mars lost it's hydrosphere.

Until further evidence is gathered and verified? I do not believe we will discover even deeply buried aquifers.
torbjorn_b_g_larsson
4 / 5 (4) Dec 10, 2017
Interesting indeed. [Disclaimer: I have worked two periods at IRF, though in Uppsala and unrelated to planetary science, and have never met Ramstad.]

To respond to the thread, there is repeated argon isotope measurement showing massive atmosphere loss as well as Curiosity observation demanding an active hydrological cycle. (And of course the suddenly juxtaposed pseudoscience cannot explain *anything*, or it would not be known as futile pseudoscience.) And there is evidence of massive amounts of buried ice from satellite and Phoenix' observations.

jonesdavid's hypothesis is both reasonable and well correlated with recent "warm volcanism" hypotheses explaining flood and clay deposits as results of dominantly high pressure CO2 rather than CO2/H2O episodes. Though the carbonate burial is up in the air, some geologists claims evidence is lacking, some AFAIK that there are impact areas with evidence of it from literary kilometers down below the lava plates.
rrwillsj
3 / 5 (2) Dec 10, 2017
tb_b_g_l, the problem I am having with your supposition is two-fold. If I am misunderstanding you? Please feel free to correct me. I know that I am as error-prone as everyone else.

First, it appears to me that you are not including the span of time. The billions of years since Mars experienced internally-driven tectonic activity and had a hydrosphere.

Second, I am not seeing inclusion of billions of years of bombardment by rock and ice. If any water is found on Mars? It will test out as remnants of cometary materials.

The Earth has the advantage over Mars, as being just a little further away from the largest congregations of asteroids. In addition to having our giant Moon as a shield.

In a Universe of fundamental uncertainty and perverse structural randomness. I think it is unrealistic for us to insist that every other planet has to mirror Earth's development.

Honestly? We are just plain spoiled by our home world and the munificence of this biosphere.
Kweden
5 / 5 (1) Dec 13, 2017
Very interesting.



If the solar wind did not strip Mars' atmosphere, then we are left with the question of how Mars lost its early atmosphere.

There is evidence that Mars collided with a very large mass at in its past. Could such a collision have stripped the atmosphere?


I agree. From what the article says is the date for loss of hydrology, it'd been solid enough to blast it all out w/out a strong m-field. Since the multiple moons indicates a large impact. But, it would've had to happen before it was too solidified or it would not have rounded back out.

Good observation. The math is more complicated.

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