earth18h
Was early Earth a purple planet? Scientists say it's possible
New research suggests Earth was once a purple planet. Early microbes used retinal, not chlorophyll, for photosynthesis.
An asteroid has a 2% chance of hitting Earth in 2032. Here’s how astronomers are tracking it
YR4 has a 2% chance of hitting Earth in 2032. Astronomers are tracking it to refine estimates of its size and orbit to see how much of a risk the space rock poses.