Two Neutron Star - Black Hole Mergers Detected

<p>About 900 million miles away in two different galaxies, a black hole and a neutron star merged, and their gravitational waves have been detected here on Earth. These detections add another type of merger to the collection so far discovered. Plus, new composition data on Mars’ south polar cap and a look back at the Tunguska Event. #AsteroidDay</p>