Once we determine that, we’ll better understand what the Trappist planets can tell usby Philip Ball / March 3, 2017 / Leave a comment
Amid all the excitement surrounding the seven Earth-like planets discovered around the pint-sized star Trappist-1 in the constellation of Aquarius, it seems surprising that there’s scant mention of how old the stellar system is. The estimate is upward of 500 million years, and it’s worth noting because, if a paper just published in Nature is correct, that’s about as long as it took for life to get started after the Earth formed.
The new work, from an international team led by Matthew Dodd and Dominic Papineau of University College London, describes structures found in Canadian rocks that they interpret as fossils of microorganisms. If that’s so, it would be possibly the earliest evidence for life on the planet: the rocks are known to be between 3770 and 4280 million years old, while our planet itself is thought to have formed about 4600 million years ago.
Identifying very ancient microfossils is always contentious. All you have to go on are ambiguous squiggles and weird-shaped structures visible in the rock under a microscope, which may have a chemical composition suggesting—but rarely proving beyond doubt—that they were produced from living things. This study will be no exception, and the team’s conclusions are already being vigorously debated.
One key feature, though, is that these mineral formations include clusters of microscopic tubes, about a fiftieth of a millimetre wide, made from iron oxide. Similar iron-oxide tubes have been reported before in the minerals found at hydrothermal vents: chimney-like geological structures on the sea bed, from which hot water warmed by volcanic magma beneath the seafloor surface streams out.
There, the tubes are formed from bacteria that transform dissolved iron into the mineral. Hydrothermal vents often support diverse ecosystems, even though they are far too deep under the sea for sunlight to drive photosynthesis. Instead, the life is sustained by the heat and the rich brew of chemicals in the hot vent water.