Most of us have witnessed a solar eclipse from here on Earth, but here's a sight you're less likely to have seen: a view of the Sun, as seen from Mars, being blocked by Phobos — the larger and closer of the Red Planet's two moons.
This remarkable view was shot by the Mastcam onboard NASA's recently landed Curiosity rover. According to the Agency, this photograph was captured using a neutral density filter that reduced the intensity of the Sun's rays by a factor of 1,000. This is a safety measure taken to preserve the camera's sensors (like human eyes, the imaging systems on Curiosity's cameras are susceptible to damage from the Sun).
There's a chance you've seen a similar photo in the past; NASA's Opportunity rover captured a video of Phobos passing in front of the Sun back in 2010. In fact, views like this are actually pretty common on Mars — we just don't always have a rover in place to watch them happen. According to Bad Astronomy's Phil Plait:
Phobos orbits Mars pretty close in, just about 6000 km (3600 miles) above the surface of Mars – compare that to the 400,000 km distance from the Earth to the Moon! Phobos is so close that it transits the Sun pretty much every day for some location on Mars, making this something of a less-than-rare event. It'll only be a year before it happens again at Curiosity's location.
Is it a simple photograph? Sure. Are eclipses relatively common on Mars? Yep. Does that make this photograph any less impressive? Absolutely not. Huge props to NASA and JPL on capturing this awesome view.