If we wanted to hide Earth from alien civilizations, could we do it? Apparently, we could, according to new work by two scientists at Columbia University.
Scientists have used fluctuations in the orbits of 3 spacecraft to map Mars' gravity. Thanks to this gravity map, it now seems likely that Mars has a molten core.
If you were standing on Mars, you could see Earth and the moon as two bright evening or morning "stars." A Mars rover captured this image of Earth in Mars' sky.
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