moon

This cylindrical projection global map is one of six new color maps of Saturn's midsized icy moons, constructed using 10 years of image data from the Cassini spacecraft. Discovered by Cassini (the astronomer) in 1684, Dione is about 1,120 kilometers across. Based on data extending from infrared to ultraviolet, the full resolution of this latest space-age map is 250 meters per pixel.

The hint comes in the form of a ratio. All elements have a certain number of known isotopes — variants of that element with the same number of protons that differ in their number of neutrons. The ratio of one isotope to another isotope is a crucial diagnostic tool.

In planetary atmospheres and surface materials, the amount of one isotope relative to another isotope is closely tied to the conditions under which materials form. Any change in the ratio will allow scientists to deduce an age for that material...

"When we looked closely at how this ratio could evolve with time, we found that it was impossible for it to change significantly," Mandt said in a press release. "Titan's atmosphere contains so much nitrogen that no process can significantly modify this tracer even given more than four billion years of Solar System history."

Via Laughing Squid:

Yummy Moon by artist Yona Lee uses 450 partially eaten Nilla Wafers to depict the different phases of the Moon. A photo on Lee's site shows the artist using a projector to map the image and match the shape of the cookies to various shapes needed to display the Moon's phases.

Jupiter's moon Ganymede is seen in transit over the great red spot. It does look like it is staring at us.