NASA Science Briefing: Comet Siding Spring at Mars

Currently setting over four hours after the Sun as seen from the heart of the UK and visible in the west-southwest at dusk, dazzling Venus is about to hit peak brightness in the constellation of Pisces. The planet attains magnitude -4.8 on Friday 17 February — some 21 times the luminosity of brightest star Sirius gracing the southeast horizon as darkness falls.

Around 3.8 billion years ago, an asteroid more than 150 miles across slammed into the Moon and created the Imbrium Basin — the right eye of the fabled Man in the Moon. New research suggests an Imbrium impactor that was two times larger in diameter and 10 times more massive than previous estimates.

New findings using data from NASA’s Mars Reconnaissance Orbiter show that gullies on modern Mars are likely not being formed by flowing liquid water. This new evidence will allow researchers to further narrow theories about how Martian gullies form, and reveal more details about Mars’ recent geologic processes.