If you’re a fan of the panspermia theory that life may have been transported to Earth on an asteroid or meteorite, then this story is for you. Researchers studying a mysterious microbe found living in volcanoes put some on a diet of nothing but meteorite material and the tiny creatures not only survived but thrived. For skeptics who wondered how a life form could survive a long trip on a space rock, here’s your answer – they ate their stone ship … leaving just enough to survive the fiery entrance through Earth’s atmosphere. Plausible? Provable? Let’s find out.
“Nanoscale resolution ultrastructural studies of meteorite grown M. sedula coupled to electron energy loss spectroscopy (EELS) points to the redox processing of Fe-bearing meteorite material. Our investigations validate the ability of M. sedula to perform the biotransformation of meteorite minerals, unravel microbial fingerprints left on meteorite material, and provide the next step towards an understanding of meteorite biogeochemistry.”
That’s research-paper-speak for “We fed some Metallosphaera sedula microbes a meteorite from Northwest Africa and it loved it.” In a paper published this week in the journal Scientific Reports, an international team of researchers explains how their search for Earth life forms that could survive on Mars led them to Metallosphaera sedula, a microbe found in sulfur-rich environments like hot springs, volcanic fields and acid mine drainage pools that have high metal ion concentrations, low pH and high temperatures … in other words, they already live on the closest thing we have to Mars on Earth.
M. sedula’s taste for heavy metal of the Periodic Table kind has led it to be used to remove iron sulphide or pyrite from coal. However, volcanoes aren’t Mars. For something closer to real extraterrestrial soil, University of Vienna astrobiologist Tetyana Milojevic and her colleagues turned to the chondrite meteorite Northwest Africa 1172 (NWA 1172). Discovered in Tabelbala, Algeria, in 2000, Milojevic told Science Alert that "NWA 1172 is a multimetallic material, which may provide much more trace metals to facilitate metabolic activity and microbial growth."
“Yummy,” said the M. sedulas. The team prepared a culture of the microbes and spread them on a sterilized slice of NWA 1172 and on a pile of pulverized powder. A control group of the microbes was fed ground-up samples of the copper-iron-sulphur Earth mineral chalcopyrite. Under microscopy, the researchers watched as the M. sedula ate more and grew faster on the meteorite meal. As they ate, the microbes emitted tiny bubbles which may have helped catalyze the metals and reduce their toxicity. When they were done feeding, the researchers could see clear evidence of where they dined, which will help determine if other meteorites carried similar metal-eating microbes to Earth.
It looks like M. sedula and other similar metal-eating microbes could live on Mars and perhaps even survive a trip on a meteor. Is this proof of panspermia? Are we the descendants of Metallosphaera sedulas?
“Our work provides a deeper insight into the biologically-mediated processing of extraterrestrial material and implications for natural samples, representing a special interest for space exploration missions.”
Was that a maybe?