We need an urgent reappraisal of how we defend the
While the concerns about our germs hitchhiking to other worlds date back to the 1950s, this week’s revelation — and its implications for the possibility of life elsewhere in the solar system — should prompt an urgent reappraisal of how we maintain the absolute integrity of both the Martian and terrestrial biospheres.
The evidence for water flowing on the red planet was gathered by the Mars Reconnaissance Orbiter, a Nasa spacecraft launched in 2005, with images that showed dark streaks down the walls of a crater. The streaks were found to carry the infrared signature of hydrated salts, which is regarded as a proxy for water.
The results were published on Monday in Nature Geoscience. They were prefigured, however, in images dating back to Mariner 9, which began orbiting Mars in 1971. These revealed a world seemingly sculpted by liquid: valleys and canyons, ancient river beds and branching canals. Even in the 1960s, Earth-based observations suggested the spectral signature of water vapour in the thin Martian atmosphere.
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