Good and bad news for astrobiologists

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Scientists have been studying the biochemistry of life on Earth for years, but how might life function outside the boundaries of our pale blue dot?

In 2010, a NASA-funded study announced the discovery of life that used arsenic, a poison to most organisms, instead of phosphorus to accomplish fundamental cell functions.

The study was criticized immediately after publication, and the journal Science, where the NASA study was published, released two studies on Sunday that “clearly” falsified the original findings.

The new studies rule out the possibility that the GFAJ-1 bacterium uses arsenic and suggest that the bacteria were exposed to trace amounts of phosphorus, unbeknownst to the researchers.

The team touted their discovery of the exotic bacterium found inside the arsenic-rich Mono Lake in California as ushering in a new era that would have altered biology textbooks and “expand the scope of the search for life beyond Earth.”

The main implication of the supposed discovery was that if life on Earth can use arsenic to survive, then there would be reason to believe that arsenic-rich environments elsewhere in the galaxy might be teeming with life.

Life on Earth is based on carbon, and scientists and science-fiction writers have been speculating for years about the other possible foundations for life that might exist outside of our planet. Silicon shares similarities with carbon and is an alternative candidate for a basic biochemical element, along with nitrogen and phosphorus.

The falsification of the NASA study may have set back research on lifeforms with exotic biochemical structures, but another set of recently published studies shows that more familiar organisms seem to be faring well in outer space.

In 2008, a shipment of organic compounds was sent to the International Space Station to test how well the organisms survived in orbit without any protection from the sun’s extreme temperature and ultraviolet radiation. For example, the lichens survived for 18 months in space by adapting to the harsh conditions. Cosmetics companies are interested in this research to use the UV resistant properties to develop sunscreen.

Another experiment that began in 2004 sent a package of worms on a Soyuz spacecraft into orbit. Upon their return to Earth, researchers discovered that the worms had increased life spans, possibly due to changes in gene expression levels.

One of the most extreme examples of life from Earth surviving in space is the tardigrade. Many of the microscopic specimens, known as water bears, were able to withstand the vacuum of space and extreme UV radiation, conditions that would instantly kill a human. After returning to Earth, the survivors could also reproduce and repair damaged DNA.