One of the Cassini mission's goals was to figure out how long a day on Saturn is. We still don't know. A new paper reports a measurement of the rotation period of Saturn that is different from past measurements.
Readers, colleagues, friends: it's finally happened. My first book is finally out in the world. Here's an excerpt that explains the design and operation of Curiosity's MMRTG, (it also applies to the future Mars 2020 rover power supply).
What is the surface of a comet like? That's one of the main questions that motivated Philae's mission to the surface of comet 67P/Churyumov-Gerasimenko. We now know the comet has a rigid crust about 10 to 50 centimeters thick, below which the comet is much more fluffy.