A Photo of the Earth and Moon from Mars!

   NASA has just released a remarkable image of the Earth and the Moon as seen from a spacecraft orbiting Mars. Our planet and Mars were 127 million miles apart when the photo was taken.

   The Mars Reconnaissance Orbiter (MRO) has been orbiting Mars since 2006, collecting very detailed close-up images and data about the surface of the red planet. In this case it was used to capture a photo of Earth and Moon with both bodies in the same frame. The image was taken at a time when the Moon was behind Earth as seen from Mars, so it shows the Earth-facing side of our natural satellite.

   Even at Mars' distance, the image of the Earth reveals continents. Australia is the reddish-brown feature in the center. Seeing ourselves as a tiny disk of light in the blackness of space can help remind us that we share a fragile and beautiful planet in our journey through space.

An Eclipse of the Sun from Mars

Our Moon is not the only astronomical body that can eclipse the Sun. In August of last year, the cameras aboard the Curiosity rover on Mars caught one of the little moons of Mars, Phobos, making an eclipse.

In the photo, you can see Phobos go across the face of the Sun. Note that the moon's shape is that of a potato (not a sphere).

Phobos is really a small moon (we believe it's an asteroid that Mars captured long ago) -- it is only about 16 miles wide in its longest dimension. The reason it covers so much of the Sun in the picture is that it orbits very close to Mars. It's only 3700 miles above the surface of the red planet.  (Compare that to the 240,000-mile distance of our own Moon!)

If you stood on the surface of Mars, Phobos would be a dim light in the night sky, rising in the west and setting in the east, and taking about 4 hours to go from horizon to horizon. (In other words, Phobos orbits Mars faster than Mars spins or rotates!)

The three black and white images of Phobos crossing the Sun were taken on Aug. 21, 2013 three seconds apart. Not a bad feat of photography by the team running the rover on its mission in Gale crater!


If you want to see Phobos better, below is a remarkable close-up photo of the little moon, taken with the Mars Reconnaissance Orbiter spacecraft, and photo processed to make the color differences more intense:

I was reminded of eclipses because I've just come back from an astronomy meeting where we discussed another August eclipse. In August 2017, our Moon will eclipse the Sun completely. The total eclipse will be visible in only one country -- the United States -- and in a band only 150 miles or so wide. Everyone else in North America will see a "partial eclipse" -- a nice bite taken out of the Sun. We estimate that 500 million people will be able to see the partial eclipse. This could become one of the most dramatic opportunities and challenges for astronomy education in our time. But we'll talk more about that in future blog posts, as the time gets closer.

A Fresh Crater Seen on Mars

The solar system is a violent place, with lots of hitting going on. Small chunks of rock and ice (left over from the formation of the planets) continue to move around the Sun and among its many worlds. When a chunk hits a planet, the pull of the planet's gravity brings the chunk in so fast, it explodes on impact, carving out a nice round crater.

We have several spacecraft orbiting and monitoring the planet Mars from above. One of them, the Mars Reconnaissance Orbiter, recently showed astronomers that a fresh crater about 100 feet (30 meters) in diameter had formed near Mars' equator sometime between 2010 and 2012. In the enhanced-color view I am sharing here, the crater looks blue because the explosion has removed a lot of the red surface dust that makes Mars the "red planet."

Careful studies of this beautiful picture have shown that the explosion of the incoming rock fragment threw material outward on Mars for more than 9 miles in all directions. You can see the magnificent dark rays of explosive material that scarred the surface when the blast happened.

New craters are being made by such impacts pretty regularly on Mars and other worlds, but it's nice to get such a detailed and recent picture from the so-called HI-RISE camera in orbit -- one of our most sophisticated instruments observing Mars.