“This means that Mars has been dry for quite a long time,” mentioned Eva Scheller, a Caltech graduate scholar who was the lead creator of the Science paper.
Today, there may be nonetheless water equal to a worldwide ocean 65 to 130 ft deep, however that’s principally frozen within the polar ice caps.
Planetary scientists have lengthy marveled at historic proof of flowing water carved within the Martian floor — gigantic canyons, tendrils of winding river channels and deltas the place the rivers disgorged sediments into lakes. NASA’s latest robotic Mars explorer, Perseverance, which landed final month within the Jezero crater, will probably be headed to a river delta at its edge in hopes of discovering indicators of previous life.
Without a time machine, there isn’t any method to observe immediately how a lot water was on a youthful Mars greater than three billion years in the past. But the hydrogen atoms floating at this time within the ambiance of Mars protect a ghostly trace of the traditional ocean.
On Earth, about one in 5,000 hydrogen atoms is a model generally known as deuterium that’s twice as heavy as a result of its nucleus accommodates each a neutron and a proton. (The nucleus of a common-variety hydrogen atom has solely a proton, no neutrons.)
But on Mars, the focus of deuterium is markedly increased, about one in 700. Scientists on the NASA Goddard Space Flight Center who reported this finding in 2015 mentioned this might be used to calculate the quantity of water Mars as soon as had. Mars in all probability began with an analogous ratio of deuterium to hydrogen as Earth, however the fraction of deuterium elevated over time because the water evaporated and hydrogen was misplaced to area, as a result of the heavier deuterium is much less prone to escape the ambiance.
The drawback with that story, mentioned Renyu Hu, a scientist at NASA’s Jet Propulsion Laboratory and one other creator of the present Science paper, is that Mars has not been dropping hydrogen quick sufficient. Measurements by NASA’s Mars Atmosphere and Volatile Evolution orbiter, or MAVEN, have confirmed that the present price, extrapolated over 4 billion years, “can only account for a small fraction of the water loss,” Dr. Hu mentioned. “This is not enough to explain the great drying of Mars.”
