Phil Plait is my favorite astronomer. He runs a blog called Bad Astronomy. Today he posted this article: Moon Photobombs Earth,  showing the moon photobombing the earth from the DSCOVR satellite.

This picture was taken from about a million miles away, at the Earth-Sun L1 Lagrangian point. That means that this satellite is always between the Earth and the Sun, and always sees a full Earth. The moon is about 400,000km away from Earth, and the DSCOVR satellite is about four times that distance away at 1.5 million km. Here is a diagram from Phil’s article.

Here are two things I find very interesting from this picture and article:

1. The Moon appears very dark here, but this is an actual picture. The Moon actually is this dark, and it only appears bright white at night because of the high contrast against the blackness of space. The Earth is more reflective than the Moon, so compared to Earth, the Moon appears darker.
2. When the Moon photobombs the Earth like this, DSCOVR will only ever see what we call the dark side of the Moon, but DSCOVR would consider this the light side of the moon. DSCOVR’s dark side of the moon is our light side, and vice versa. The Moon is tidally locked with the Earth, so the moon rotates only one time for every revolution it makes around the Earth. Compare this to the Earth which is not tidally locked to the Sun, and makes 365 rotations for every 1 revolution of the Sun. If the Earth was tidally locked, we would have a radically different climate.

It is a very exciting time in Astronomy. Two weeks ago, we had never seen Pluto close up. In fact, this was the best picture we had of Pluto:

Some people didn’t even realize this because a simple google search on just about any astronomical object will always pull up a nice “picture”. These pictures are usually just an artist’s rendition of what they think the object may look like. There was a time when all of the planets were nothing more than dots to our naked eyes, and small disks to a telescope. Through a telescope, Galileo discovered the four Gallilean moons of Jupiter, but I bet he never would have guessed that Jupiter has over 60 moons! Even with the power of the hubble telescope, we were only able to see Pluto and Charon as a set of a few pixels. It took an interplanetary mission to get these pictures.

Before anyone had seen Pluto in any significant resolution, I suspect they would have pictured it much like the Moon, or Mercury, a lifeless cratered dusty body. Here is a picture of mercury in greyscale. Nothing too impressive, just lots of craters and rays extending out from the craters, maybe a few cracks.

These are the best pictures we have of Nix and Hydra. I expect that we will get slightly better pictures in the months to come, but probably nothing too astounding. Their shape, orbits, rotations, and even colors are all very interesting. I’m excited to learn more about them.

Pluto has blown our low expectations out of the water. It is far from a lifeless body. It has a slight atmosphere, it has snow/ice, it has mountain ranges, it has ice plains, and strangest of all, it appears to have no impact craters much like the Earth! For a planet to have no impact craters it either has to have no impacts, which is highly unlikely, or it has to be geologically active, resurfacing itself. Scientists believe that the surface of Pluto is only 100 million years old!

Who knows what tomorrow has in store for us!

http://www.wired.com/wiredscience/2013/08/curiosity-value/