NASA's Mars Atmosphere and Volatile Evolution (MAVEN) mission has been gathering information on Mars' upper atmosphere, ionosphere, and solar and solar-wind interactions since its orbit insertion in September 2014. On November 5th the first MAVEN results were published in a special issue of Geophysical Research Letters . The issue contains over 40 articles investigating measurements of the overall geometry and variability of the Martian magnetosphere, upper atmosphere, and ionosphere and their responses to interplanetary coronal mass ejections and solar energetic particle influxes, with the highlights covered in the introductory article. NASA also held a news briefing discussing the results.
One of the many results presented was the identification of the process that transitioned the Martian climate from warm and wet to cold and arid. MAVEN has measured the rate at which the solar wind is stripping the Martian atmosphere of gas:
"Mars appears to have had a thick atmosphere warm enough to support liquid water which is a key ingredient and medium for life as we currently know it," said John Grunsfeld, astronaut and associate administrator for the NASA Science Mission Directorate in Washington. "Understanding what happened to the Mars atmosphere will inform our knowledge of the dynamics and evolution of any planetary atmosphere. Learning what can cause changes to a planet's environment from one that could host microbes at the surface to one that doesn't is important to know, and is a key question that is being addressed in NASA's journey to Mars."
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One of the primary drivers for the distinct lack of a Martian atmosphere is believed to be the loss of atmospheric molecules that are stripped away by the passing solar wind. A strong planetary magnetic field would divert the solar wind around the planet and protect the Martian atmosphere. The MAVEN spacecraft confirmed this is happening, and some interesting ideas have been floated to mitigate the effect.
A recent paper published in JGR: Space Physics used Magnetohydrodynamic (MHD) models to investigate the magnitude of the effect on atmospheric retention that a magnetic field would have on Mars and found a very interesting result. Their models confirmed that the rate of atmospheric loss was six times higher for a planet with no magnetic field compared to a planet with a strong magnetic field; however, they found the highest rate of atmospheric loss was actually when there was a weak magnetic field.
But the highest rate of atmospheric ion loss was with a weak magnetic field—6 times faster than with no magnetic field at all. The team found the reason was the magnetic field lines, which guide the motion of charged particles, were easily blown back by the solar wind, creating a path for these ions to escape into space above Mars's nightside. This means that instead of providing a small measure of protection, Mars's remnant magnetic field could actually have sped the planet's transformation into the cold, barren world it is today.
Research Paper: Sakata, et al., Effects of an Intrinsic Magnetic Field on Ion Loss From Ancient Mars Based on Multispecies MHD Simulations, Journal of Geophysical Research: Space Physics, https://doi.org/10.1029/2019JA026945, 2020
(Score: -1, Flamebait) by Anonymous Coward on Thursday November 12 2015, @01:03AM
This is a decent post. And it gets no comments.
But then, it's very speculative stuff. And it's couched in a cautious tone (as science generally should be) such that AGW warriors are unaware/too confused to know if they should go pounce and rant about the end of world and how we should all repent. But then AGW warriors tend to be social warriors rather than a science sort.
Basically, SN readership is nothing like they/we pretend to be, i.e., science-literate.
(Score: 1, Interesting) by Anonymous Coward on Thursday November 12 2015, @04:04AM
Yeah, it's much too late to tell the Venusians and the Martians to strengthen their planets' magnetic fields (not to mention gravity, tsk) so water and air won't escape to space so quickly.
As for the people of Earth, we've been ignoring scientists in regard to the warming effect of carbon dioxide since 1896, when Svante Arrhenius wrote about it (http://warming.sdsu.edu/arrhenius_paper_1896.pdf). Odds are we'll continue to do so even if the bulk of the human population winds up living in Antarctica. :-)
That metallic ionospheric layer that MAVEN found, that's neat, though. They measured the way it blocks (occults) radio waves, but I wonder how it does at reflecting them. The reflected waves could be used for communication, like we do with shortwave radio on Earth. What did you find interesting about the article?