Mars May Be Even Wetter Than It Was Last Week

By Keith Cowing
June 27, 2000
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Mars May Be Even Wetter Than It Was Last Week
Mars as seen by Viking — NASA

In less than a week, our collective understanding of the amount of water on Mars has been totally revamped. First there was the announcement that liquid water is apparently at work just below the surface of Mars – possibly even to this very day.

A day later it was announced that analysis of a Martian meteorite provided clear evidence that Mars once had salty oceans similar to those on Earth. Now another announcement (also based on analysis of a Mars meteorite) has been made that the amount of water present on Mars may be several times greater than what was previously thought (last week).

According to a press release by the American Geophysical Union, “The crust of the planet Mars may hold two to three times more water than scientists had previously believed. This finding is based on a study by Dr. Laurie A. Leshin of Arizona State University, comparing the amount of deuterium, an isotope of hydrogen, found in a meteorite of Martian origin to the amount found in the Martian atmosphere. Her report will be published in Geophysical Research Letters on July 15. “

These claims are based upon studies of deuterium vs hydrogen ratios on Mars. Deuterium is a heavy isotope of hydrogen. Over time, water breaks into hydrogen and oxygen through the process of photodissociation. Hydrogen is the lightest element and can readily escape from a small planet’s atmosphere. Deuterium, a bit heavier (it has an extra neutron), escapes readily albeit at a slower rate. The difference in the rates of escape and the current levels of deuterium can be used to determine the amount of water on Mars in the past as well as today.

This assumes that the process has been happening in a similar fashion over time.
According to the press release “scientists had previously assumed that before the deuterium level was enhanced by the escape of hydrogen, Martian water more closely resembled that on Earth, with a comparable ratio of deuterium to hydrogen. In order to reach the current value of five times higher than Earth’s water, they calculated that around 90 percent of the water in the Martian atmosphere and upper crust had been lost over the planet’s history. “

Dr. Laurie A. Leshin of Arizona State University sought to understand the amount of water on Mars by examining Mars meteorite QUE94201, a small sample collected in Antarctica in 1994. Small hydrated crystals were found within the meteorite. According to the press release “these crystals contain hydrogen from the Martian interior, which was not affected by atmospheric escape. They revealed a smaller percentage of deuterium than current Martian atmospheric measurements.”

Leshin looked at the current mechanisms whereby hydrogen would escape from Mars and what conditions were like when the solar system (and Mars) was much younger. According to Leshin’s model, a higher ultraviolet radiation flux from a much younger sun would have led to hydrogen loss early in the planet’s history. She implies that this might mean that the water on Mars today is due largely to eons of cometary bombardment since comets have a similar deuterium to hydrogen ratio.

According to the press release, Dr. Leshin concludes that “since Martian water originally contained higher deuterium levels than previously thought, the Martian atmosphere has lost two to three times less water through the eons in order to arrive at the isotope’s current atmospheric level. That water should still exist today on Mars, she says, located within the planet’s crust. In fact, evidence from this and previous research on Martian meteorites supports the idea that a significant Martian groundwater reservoir currently exists.

After a week of back-to-back water on Mars stories it now seems that there may well be liquid water at work on Mars, that Mars has more water than we thought, and that it once had oceans like our own.

I wonder what is in store for next week’s cache of Mars news?

Related Links

° Mars may hold twice as much water as previously thought, American Geophysical Union
° Meteorite research indicates Mars had Earth-like oceans, Arizona State University
° QUE94201 Sample Summary, NASA JSC
° The QUE 94201 Meteorite, NASA JPL
° QUE94201 Meteorite (Adobe Acrobat), Mars Meteorite Compendium

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