Billions of years ago, Mars had flowing water, ice, and clouds, and then lost most of it. The latest study from NASA’s MAVEN Mars orbiter shows that it is still losing water, but the “leak” is not constant.
The craft has been studying the atmosphere of the Red Planet over an entire Martian year, and discovered that the rate of loss varies wildly up to a factor of 10, with solar irradiation and seasonal changes possible causes of the differences.
“MAVEN’s findings reveal what is happening in Mars’ atmosphere now, but over time this type of loss contributed to the global change from a wetter environment to the dry planet we see today,” said Ali Rahmati, a MAVEN team member at the University of California, Berkeley, in a statement.
The water loss is estimated by measuring the amount of hydrogen leaving the upper atmosphere. Sunlight breaks water vapor molecules, forming oxygen and hydrogen. Hydrogen moves to the upper atmosphere, where it then escapes Mars.
The scientists suspect the Sun's activity, seasonal variation on the planet, and Mars’ elliptical orbit play a role in these changes, although it’s not clear which is the dominant factor.
This fluctuating escape had previously been observed by the Hubble Space Telescope and by ESA’s Mars Express orbiter, but MAVEN’s detections are the first to come from a continuous tracking campaign.
“Now that we know such large changes occur, we think of hydrogen escape from Mars less as a slow and steady leak and more as an episodic flow – rising and falling with season and perhaps punctuated by strong bursts,” added Michael Chaffin, a scientist at the University of Colorado at Boulder.
Chaffin is presenting the results at the joint meeting of the Division for Planetary Sciences and the European Planetary Science Congress in Pasadena, California, this week.
MAVEN is using a suite of instruments to track the minutest details of Mars' atmosphere. The scientists hope that more observations over the next few years will clarify what phenomenon is responsible for Mars’ water loss.
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