NORTHERN AUTUMN BEGINS TODAY: Today, the sun is crossing the equator heading south, changing seasons ... for the better, according to aurora watchers. Autumnal cracks in Earth's magnetic field allow solar wind to penetrate more easily than usual, sparking geomagnetic activity. Indeed, today began with a G1-class geomagnetic storm. Arctic sky watchers should be alert for the first auroras of autumn after nightfall. Free: Aurora Alerts

ROBOTS LAND ON ASTEROID RYUGU: Today, Japan made history by landing two rovers onto the surface of an asteroid. The two rovers (named Rover-1A and 1B) fell from their mothership, Hayabusa2, less than 100 meters above diamond-shaped asteroid Ryugu. Now they are hopping across the rocky landscape in an unprecedented feat of exploration. This picture was taken by Rover-1A in mid-hop:

Hopping is necessary because the asteroid's gravity is too weak for simple rolling.  Instead of wheels, the rovers have rotating motors inside that allow them to shift their momentum and, thus, make little jumps across the asteroid's rugged surface. Mission controllers are taking great care that the rovers, which measure 18 cm by 7 cm and weigh only 1 kg, do not fly into space.

As historic as this achievement is, it is only the beginning: The two rovers are on a reconnaissance mission for two more robots slated to land later this year.  In October, Hayabusa2 will release MASCOT (Mobile Asteroid Surface Scout), a larger lander made by the German Aerospace Center. MASCOT will be followed, in turn, by another Japanese robot.

Above: Hayabasa2 photographs its own shadow on the asteroid. Credit: JAXA