We end the year on a slightly melancholic note. NASA has officially retired the Mars InSight lander after failing to re-establish contact.

Unlike the rovers, InSight was a stationary geology lab. For the last four years, it sat quietly on the Elysium Planitia, listening to the heartbeat of the planet. It detected over 1,300 "marsquakes" and mapped the deep interior crust, mantle, and core of the Red Planet for the very first time.

Sadly, the relentless Martian dust slowly coated its solar panels, and the harsh winter finally drained its batteries. It completed its primary mission and leaves behind a wealth of data that geologists will be studying for decades. A job well done.