It may not look much, but these are the first images of Comet C/2013 A1, known as Siding Spring, as it passed by Mars on Sunday. The images were captured by NASA's Mars Reconnaissance Orbiter.
The comet passed closer to Mars than any comet has ever passed by Earth in recorded history — so scientists are excited to see what the craft orbiting Mars made of it. Believe it or not, this is the "highest-resolution views ever acquired of a comet coming from the Oort Cloud at the fringes of the solar system".
What does it reveal? Well, the images, which were taken from a distance of 86,000 miles, show the size of the comet's nucleus to be under a quarter of a mile across. That's just half the size of previous predictions. We'll have to wait to see more images of the rare event before we find out more. [NASA]