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Patience in scientific discovery

Published: December 6, 2012
Section: Opinions, Top Stories


NASA recently released their findings of soil samples from Mars but only after initially peddling back from their original claims. In the past month, speculation surfaced that NASA’s Curiosity rover discovered evidence potentially unveiling the possibility of life on Mars.

In an interview with NPR on Nov. 13, the mission’s chief scientist, John Grotzinger, called implicit evidence in recent data sent back from the Mars rover, “one for the history books.”

To the amateur scientists of the world, the news sounded striking. The suggestion of possible contamination appeared indicative of the discovery of organic molecules.

Naturally, NASA had to review the data for accuracy and ensure that contamination from earth had no influence. The process took nearly a month and while the discovery has not yet been completely verified and the carbon could still be contamination from Earth, NASA officials felt comfortable enough to announce the findings.

During the wait, however, NASA backpedaled on their claims for fear of creating too great an expectation. In an attempt to clear up misconceptions, Media Manager Veronica McGregor tweeted, “What did I discover on Mars? That rumors spread fast online. My team considers this whole mission one for the history books.”

While finding organic molecules on Mars may be indicative of life, it is not necessarily so. Previous missions to Mars reported data that seemed to exhibit—when met with certain chemicals—that Martian soils released gasses similar to those released during the process of cellular respiration. This can be attributed to life or it can be attributed to the high energy UV light that permeates the Martian atmosphere, making chemistry on Mars much unlike that on Earth.

The device used by Curiosity to make this claim is called SAM, or Sample Analysis at Mars. SAM is built to look for organic compounds including methane. It also seeks to sort out the heavier isotopes.

The presence of carbon on Mars is not necessarily indicative of life. Likely enough, contamination could have been brought in by asteroids. It is not as though we have not been searching for carbon on Mars for a long time. What the Curiosity rover brings to the table in SAM is the ability to search for organic compounds of microbial life. Yet these have been found before and even now it is difficult to determine whether they are the product of life or strange Martian chemistry. It will be some time before NASA can sort out whether the Martian carbon was created on Mars. Even then, more is necessary to prove evidence of life than simply carbon.

Organic molecules can also exist without the presence of life. NASA states that “the search for organic molecules is particularly important in the search for life on Mars, because life as we know it cannot exist without them, though they can exist without life.”

But what if life exists in a form that is not as we know it? Andreas Rauch, an astrophysics Ph.D. student at Brandeis, explained that the issue with the Mars rover technology is that by the time a rover reaches Mars, its ability to discern life is already out of date with our current understanding of life. This is largely because the plans for the rover take so long to be realized after their conception.

The SAM technology, however, is specifically built for detecting the possibility of life. Methane is by no means a rare element in our solar system or throughout the exo-planets at which we’ve looked. But being able to sort out the heavier isotopes of carbon is a useful tool.

The ratios of heavy elements to their normal states is essentially a determined value by solar nucleosynthesis, Professor John Wardle (PHYS) said. Through this process, elements are generated in stars. If the atmospheric ratio deviates from the solar expected ratio, this can help us determine when Mars lost its atmosphere. This is done under the assumption that over time the lighter isotopes would have escaped the atmosphere more frequently. Mars likely lost its atmosphere when it became exposed to solar winds, which would have happened when Mars lost its magnetic field.

SAM is equipped with a gas chromatograph, a quadruple mass spectrometer and a tunable laser spectrometer. The gas chromatograph sorts out gasses, separating them by mass. The quadruple mass spectrometer is capable of sorting gasses by molecular weight and also capable of identifying them. It receives the gases from the chromatograph. The tunable laser spectrometer analyzes which wavelengths of light are absorbed by the atmosphere in order to determine the ratios and concentrations of chemicals important to life. These tools work together for the sole purpose of detecting the possibility of life, whether present or past, on Mars.

The evidence announced by NASA, though, doesn’t prove the existence of green men or even single-cell organisms. Carbon is important but we are left with little more than we started: a possibility.

The Curiosity rover is well-named; the possibility of life on Mars continues to pique our curiosity. But we must also be patient. We may never be gratified with full proof of even the faintest possibility of extraterrestrial life.