This heart-shaped pit on Mars is within Acheron Catena, one of many fissures on the eastern flank of Alba Patera. The heart is about 2.3 kilometers across at its widest. It was first noticed in a MOC image from Mars Global Surveyor; this image is from CTX on Mars Reconnaissance Orbiter and has a resolution of 6 meters per pixel.
I can't take credit for discovering this feature; credit for noticing it goes to Malin Space Science Systems, who used to post lots of photos of funny-cool things from Mars while Mars Global Surveyor was active. Here's the a MOC image containing the heart. Knowing how much of Mars has now been imaged by the Context Camera (CTX) on Mars Reconnaissance Orbiter (well over half), I figured that a little searching on ASU's Global Mars Data website would lead me to the feature, and it did; so the image above is from CTX and has a resolution of 6 meters per pixel. How did the heart form? To answer that, let's pull back and look at the context (something that CTX -- as you can tell from its name -- was designed for):
NASA / JPL / MSSS
Chain of pits (including a heart) within Acheron Catena
At the center of this image is a heart-shaped pit within Acheron Catena, one of many fissures on the eastern flank of Alba Patera on Mars. The heart is about 2.3 kilometers across at its widest. It was first noticed in a MOC image from Mars Global Surveyor; this image is from CTX on Mars Reconnaissance Orbiter.
There is a lot of interesting geology going on in this picture. The heart and the circular pits that occur within Acheron Catena are all collapse pits, which formed when the ground literally opened up beneath the surface, part of extensive extensional faulting that you can see all around the flanks of Alba Patera, one of Mars' great big volcanoes. Underneath that extensional faulting you can see lots and lots of volcanic landforms -- the lobate fronts of lava flows, and sinuous channels that once contained molten rock but which are now just full of dust. So, Happy Valentine's Day! And it's not too late to buy a Valentine's gift through our Facebook Cause, which nets the Planetary Society $10 for every purchase.