Everyone’s heard of Jupiter’s four most famous moons Europa, Io, Callisto, and Ganymede—we’ve known about them for over 400 years, thanks to Galileo—but giant Jupiter has many more moons than that. To date there are thought to be 69 natural satellites orbiting Jupiter. 53 are officially named, while 16 are awaiting further confirmation. So you’d be forgiven for not being immediately familiar with all of them…it’s a big Jovian family!
The little world seen above is one of Jupiter’s smaller and lesser-known satellites and it holds a particular distinction. It’s called Metis (pronounced like “meet” in the present tense, not “met” in the past) and it’s only about 37 miles across and 21 miles high. It is the closest moon to Jupiter, orbiting within the planet’s main ring (yes, Jupiter has rings) at a distance of about 80,000 miles. It’s also Jupiter’s speediest moon—at 70,500 mph it completes a single orbit in just over 7 hours. That’s almost three hours less than a Jovian day!
This animation is comprised of three images acquired by ESA’s Mars Express spacecraft on Sept. 12, 2017 with its High Resolution Stereo Camera (HRSC). It shows parts of the grooved and pitted surface of Phobos, the larger of Mars’ two natural satellites.
Can you feel the heat? NASA’s Mars Odyssey can see it! This is an image of Mars’ smaller moon Deimos, captured with Odyssey’s THEMIS (Thermal Emission Imaging System) instrument on Feb. 15, 2018. Part of the 7-mile-wide Moon was in shadow, but the sunlit surface area reached temperatures up to 200 K (that’s still pretty cold for us, though… –100ºF / -73ºC!)
That’s here; that’s home; that’s us—the two bright objects in this picture are Earth and the Moon, imaged by NASA’s OSIRIS-REx spacecraft on January 17, 2018 from a distance of 39.5 million miles (63.5 million km).
This is about the distance between Earth and Mars at their closest points to each other (give or take about 6 million miles) or about 165 times farther away from us than the Moon.
“We came all this way to explore the Moon, and the most important thing is that we discovered the Earth.”
– William Anders, Apollo 8 Commander
On Christmas Eve, December 24, 1968, the Apollo 8 CSM entered orbit around the Moon and, after completing 4 full orbits, provided the three astronauts on board with an amazing sight: a blue Earth rising* beyond the Moon’s cratered limb. Commander Frank Borman spotted the scene first and, after taking a 70mm black-and-white photograph, was able to rotate the Command Module so Earth remained in view through the small windows while CM pilot Jim Lovell captured this famous image on color film. It was the first time any humans saw the Earth from the vicinity of the Moon…and it was also the first Christmas that astronauts spent in space.
“The vast loneliness is awe-inspiring and it makes you realize just what you have back there on Earth,” Jim Lovell said.