October 16, 2013
Curiosity Sampling Confirms Earth Meteorites Are From Mars
[ Watch the Video: Martian Roots In Many Meteorites ]
Lee Rannals for redOrbit.com - Your Universe Online
A new measurement of Mars' atmosphere by Curiosity's Sample Analysis at Mars (SAM) instrument shows two forms of argon gas. The lighter and heavier forms, or isotopes, of argon exist naturally throughout the Solar System, but on Mars the ratio of light to heavy is skewed because the planet lost its original atmosphere to space.
Past analyses of gas bubbles trapped inside Martian meteorites have narrowed the Martian argon ratio to between 3.6 and 4.5. Measurements taken by NASA's Viking landers in the 1970s put the Martian atmospheric ratio to between four and seven, but the latest SAM measurement shows the planet at an argon ratio of 4.2.
“We really nailed it,” Sushil Atreya of the University of Michigan, Ann Arbor, lead author of a paper published today in Geophysical Research Letters, said in a statement. “This direct reading from Mars settles the case with all Martian meteorites."
Determining the planet's atmospheric loss would enable scientists to better understand how Mars transformed from a once water-rich planet to the drier, colder and less hospitable one that it is today.
Atreya said if Mars had held on to its original argon, its ratio of the gas would be the same as that of the Sun and Jupiter, which have so much gravity that isotopes cannot preferentially escape.
Argon only represents a small fraction of the gases lost to space from Mars, but because it is a noble gas it does not react with other elements or compounds, making it a good tracer for knowing the history of the Martian atmosphere.
“Other isotopes measured by SAM on Curiosity also support the loss of atmosphere, but none so directly as argon,” Atreya said. “Argon is the clearest signature of atmospheric loss because it’s chemically inert and does not interact or exchange with the Martian surface or the interior. This was a key measurement that we wanted to carry out on SAM.”
NASA has not had a chance to comment on the team's finding because the US space agency is still under the grip of the government shutdown. However, a Senate deal was reached on Wednesday, so the US space agency will soon be opening its doors once again, as well as its newswires.