The NASA rover Curiosity has collected enough evidence to finally prove that certain meteorites on the Earth which are claimed to come from Mars indeed did come from the Red Planet.
Curiosity did this by measuring the components of the Martian atmosphere. The results the rover came up with will be utilized to confirm if a meteorite believed to have originated from Mars came from there, or if it actually came from some other source.
According to the data that Curiosity has collected, the key to distinguishing a Martian meteorite from other sorts is argon gas. Actually, two types of argon gas, to be exact — Argon 36 and Argon 38.
Curiosity’s Sample Analysis at Mars, or SAM, instrument, scientists found, was able to analyze the difference between the ratios these lighter and heavier amounts of argon gases appear in the Martian atmosphere. The Martian atmosphere contains much more Argon 38 gas, as it’s heavier and didn’t get lost into space to the extent that the Argon 36 gas did.
Scientists have previously measured the amounts of both of these argon gases trapped in air pockets in meteorites thought to have originated from Mars. They discovered an argon ratio of 3.6-4.5, and then hypothesized that the amount of argon gas in the atmosphere of Mars must be around 4 percent.
In the 1970s, NASA’s Viking landers measured the amount of argon gas and at that time, determined it make up anywhere between 4-7 percent of the Martian atmosphere. However, SAM’s measurements have been much more precise, and measured the ratio to be 4.2 percent.
On Wednesday, Geophysical Research Letters (a journal of the American Geophysical Union) published the findings. The lead author, from the University of Michigan, was Sushil Atreya.
Atreya was enthused at learning how close scientists were in determining the correct ratio of argon gas in the Martian atmosphere. She stated: “We really nailed it,” adding that the data Curiosity obtained “settles the case with all Martian meteorites.”
If Mars still retained as much argon gas as it once had, would it really be more hospitable?
Mars may once have been far wetter, warmer, and more hospitable than it is today; but, not because of the amount of argon gas that used to be in it’s atmosphere. According to Atreya, if Mars had managed to hold onto its atmosphere better, it would have the same ratio of argon gas as Jupiter and the Sun has. The gravity of both is so strong that it even prevents isotopes from preferentially escaping.
One other reason that the ratio of argon is used by scientists who are interested in discovering more about how Mars was like in the past is that it’s a noble gas. Argon gas doesn’t react with other compounds or elements, being chemically inert, so any difference in the amount of it now compared to the past is directly due to the loss of the overall atmosphere of Mars throughout the history of the Red Planet.
NASA is still shut down, along with the rest of the government, though the shutdown might be over as early as tomorrow — at least, until January, when the government might be facing a shutdown all over again.
But, just because NASA is shut down, doesn’t mean that Curiosity has stopped working, nor the Juno probe, which is on its way to Jupiter.
Which meteorites on the Earth originated from Mars? Thanks to the Curiosity rover, and the noble gas argon, we may soon know.
Written by: Douglas Cobb