We already knew about Venus. We had our suspicions about Mars. Now we're sure.
Our two closest solar system neighbors once had oceans – planet-encircling, globe-girdling, Earth-like oceans. But waterbearing planets are fragile. Venus didn't have the right stuff and lost her oceans to space. We have the smoking gun. And now we know that Mars, also, poor Mars, couldn't hold on. Mars has lost to space at least 80% of all the water it once had.
The supermassive black hole is 40 million times as massive as the sun and powers a quasar that existed 700 million years after the Big Bang.
The asteroid zoomed by Earth at a perfectly safe distance of around 1.8 million miles (2.9 kilometers).
Images show surprise changes to the spacecraft as it interacted with the atmosphere.
