Is there life on Mars?(3)
2023-05-30 来源:百合文库
All being well, Perseverance will follow soon from America’s principal spaceport, at Cape Canaveral, in Florida. This one tonne, six-wheeler, which cost $2.4bn to build and launch and will take another $300m to operate during its mission, will be the most sophisticated vehicle yet sent by America to the Martian surface.
Jezero, the crater around which it will trundle, sits on the inner rim of Isidis Planitia, one of the largest impact basins on Mars, which was excavated 3.9bn years ago. One source of the water which formed the lake that once lay within Jezero seems to have been a river leading to a well-preserved delta (see picture). The layers of sediment in this feature are prime targets in the search for Martian biology.
On Earth, some of the oldest evidence for life comes in the form of stromatolites. These stratified structures form in shallow water when colonies of microbes grow layer upon layer, trapping minerals as they do so. The most ancient examples are thought to be those found in Greenland in 2016, which have been dated to 3.7bn years before the present day. If there was sufficient time for stromatolite-forming organisms to evolve on Earth by this date then there is no obvious reason why they might not also have evolved on Mars.
Jezero, the crater around which it will trundle, sits on the inner rim of Isidis Planitia, one of the largest impact basins on Mars, which was excavated 3.9bn years ago. One source of the water which formed the lake that once lay within Jezero seems to have been a river leading to a well-preserved delta (see picture). The layers of sediment in this feature are prime targets in the search for Martian biology.
On Earth, some of the oldest evidence for life comes in the form of stromatolites. These stratified structures form in shallow water when colonies of microbes grow layer upon layer, trapping minerals as they do so. The most ancient examples are thought to be those found in Greenland in 2016, which have been dated to 3.7bn years before the present day. If there was sufficient time for stromatolite-forming organisms to evolve on Earth by this date then there is no obvious reason why they might not also have evolved on Mars.
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