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European Space Agency

An Italian team of scientists says it has strong evidence of a subsurface lake of liquid water on Mars. It's a discovery that adds to the speculation that there could once have been life on Mars — and raises the possibility that it might be there still today, since liquid water is an essential ingredient for life.

Wednesday was the day astronomers said goodbye to the old Milky Way they had known and loved and hello to a new view of our home galaxy.

A European Space Agency mission called Gaia just released a long-awaited treasure trove of data: precise measurements of 1.7 billion stars.