Impact Gardening Churns Surface of Saturn’s Moon Europa

<p>Over tens of millions of years, the surface of Europa has been churned by impacts down to an average depth of 30 centimeters. This churning means that the search for chemical biosignatures must look below that zone. Plus, methane and icequakes at Enceladus, predicting underwater eruptions, Virgin Galactic's flight, and a Chinese spacewalk.</p>