Posted on by Jason Major

Is This Proof of Life on Mars?

View of Mars from Viking 2 lander, September 1976. (NASA/JPL-Caltech)

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The Curiosity rover is currently on its way to Mars, scheduled to make a dramatic landing within Gale Crater in mid-August and begin its hunt for the geologic signatures of a watery, life-friendly past. Solid evidence that large volumes of water existed on Mars at some point would be a major step forward in the search for life on the Red Planet.

But… has it already been found? Some scientists say yes.

Researchers from universities in Los Angeles, California, Tempe, Arizona and Siena, Italy have published a paper in the International Journal of Aeronautical and Space Sciences (IJASS) citing the results of their work with data obtained by NASA’s Viking mission.

The twin Viking 1 and 2 landers launched in August and September of 1975 and successfully landed on Mars in July and September of the following year. Their principal mission was to search for life, which they did by digging into the ruddy Martian soil looking for signs of respiration — a signal of biological activity.

A six-inch-deep trench in the Martian soil dug by Viking 1 in February 1977. The goal was to reach a foot below the surface for sampling.

The results, although promising, were inconclusive.

Now, 35 years later, one team of researchers claims that the Viking landers did indeed detect life, and the data’s been there all along.

“Active soils exhibited rapid, substantial gas release,” the  team’s report states. “The gas was probably CO2 and, possibly, other radiocarbon-containing gases.”

By applying mathematical complexities to the Viking data for deeper analysis, the researchers found that the Martian samples behaved differently than a non-biological control group.

“Control responses that exhibit relatively low initial order rapidly devolve into near-random noise, while the active experiments exhibit higher initial order which decays only slowly,” the paper states. “This suggests a robust biological response.”

While some critics of the findings claim that such a process of identifying life has not yet been perfected — not even here on Earth — the results are certainly intriguing… enough to bolster support for further investigation into Viking data and perhaps re-evaluate the historic mission’s “inconclusive” findings.

The team’s paper can be found here.

Image credits: NASA/JPL-Caltech. Also, read more on Irene Klotz’s article on Discovery News.

Posted on by Nancy Atkinson

Replication of Arsenic Life Experiment Not Successful So Far

A replication of the arsenic life experiment being done by biologist Rosie Redfield. Image credit: Rosie Redfield.

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One of the most vocal and ardent critics of the so-called ‘arsenic life’ experiment which was published in December 2010 was biologist Rosie Redfield from the University of British Columbia in Vancouver. The science paper by NASA astrobiologist Felisa Wolfe-Simon and her team reported that a type of bacteria in Mono Lake in California can live and grow almost entirely on arsenic, a poison, and incorporates it into its DNA. Redfield called the paper “lots of flim-flam, but very little reliable information.” Her opinion was quickly seconded by many other biologists/bloggers.

Redfield has been working on replicating the experiment done by Wolfe-Simon, and doing in her work in front of the world, so to speak. She is detailing her work in an open lab notebook on her blog. So far, she reports that her results contradict Wolfe-Simon et al.’s observations.

To date, Redfield is finding that the bacteria, called GFAJ-1, is not living and growing in arsenic, but dying. Redfield says her work refutes that cells from the GFAJ-1 could use arsenic for growth in place of phosphorus, and when arsenic was added to the low-phosphorus medium in which the bacteria was living, the bacteria was killed. Additionally, in other test viles, the growth properties Redfield is finding for GFAJ-1 don’t match those reported by Wolfe-Simon and her team, which claimed that the bacteria could not grow on a low concentration of phosphorus, and that the bacteria could grow on arsenic in the absence of phosphorus.

Felisa Wolfe-Simon, right, a NASA astrobiology research fellow in residence at the USGS, and Ronald Oremland, an expert in arsenic microbiology at the USGS, examine sediment in August 2009 from Mono Lake in eastern California. Credit: © 2009 Henry Bortman

Redfield’s two major early criticisms of the original paper were that the authors had not ruled out the possibility that the bacteria were feeding on phosphorus contaminating their growth medium; and that the bacterial DNA was not properly purified, so that the arsenic detected might not actually have been in DNA.

An article in Nature reports that other researchers also working on replicating the experiment with GFAJ-1 laud Redfield’s efforts, but say it is too early to conclude that she has debunked the original work.

Additionally, one problem is that Redfield she did not replicate the experiment exactly, as she had to add one nutrient not used by the authors of the original arsenic life paper in order for the bacteria to grow.

This is not the first time scientists have written open notebooks during the replication of controversial findings, but it might be one of the more notable, given the amount of media attention the arsenic life paper received.

Redfield is also hoping that her work will highlight the benefits of open notebook-type research.

You can read Redfield’s blog about her work at this link.

Sources: Nature, Redfield’s blog.