The hills may not be alive, but they are moving. The comet 67P/Churyumov-Gerasimenko has small cliffs that migrate across the landscape for months at a time.
The European Space Agency’s Rosetta spacecraft arrived at 67P in 2014 and orbited the comet for two years. The pictures it took revealed a changing landscape, especially when the comet reached its closest approach to the sun, and jets of dust and gas were seen shooting off the surface into space.
The jets form when sunlight hits the surface …
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