Do you wonder how astronomers find all those exoplanets orbiting stars in distant solar systems?
Mostly they use the transit method. When a planet travels in between its star and an observer, the light from the star dims. That’s called a transit. If astronomers watch a planet transit its star a few times, they can confirm its orbital period. They can also start to understand other things about the planet, like its mass and density.
The planet Mercury just transited the Sun, giving us all an up close look at transits.
Welcome back to another installment in the “Definitive Guide to Terraforming” series! We complete our tour of the Solar System with the planet Mercury. Someday, humans could make a home on this hostile planet, leading to the first Hermians!
The planet Mercury is an intensely hot place. As the nearest planet to our Sun, surface temperatures can get up to a scorching 700 K (427° C). Ah, but there’s a flip-side to that coin. Due to it having no atmosphere to speak of, Mercury only experiences intensely hot conditions on the side that is directly facing the Sun. On the nighttime side, temperatures drop to well below freezing, as low as 100 K (-173° C).
Due to its low orbital period and slow rate of rotation, the nighttime side remains in the dark for an extended period of time. What’s more, in the northern polar region, which is permanently shaded, conditions are cold enough that water is able to exist there in ice form. Because of this, and a few reasons besides, there are many who believe that humanity could colonize and even terraform parts of Mercury someday.
Big Bird has been grabbing the headlines lately, and its time for another Muppet to get a little face time. So, here’s Cookie Monster’s face, plastered across the surface of Mercury. Well, it looks like it, anyway. This is an image from the MESSENGER spacecraft, orbiting Mercury, and the folks at Goddard Space Flight Center suggested this superposition of younger craters on older craters (in this case two smaller and shadowed craters that look like googly eyes placed on the rim of an older crater) appears to resemble everyone’s favorite blue, Sesame Street, cookie-loving monster.
While most of us can enjoy this image for the pareidolia effect of seeing a familiar face (and start salivating about cookies), what scientists are looking at here are craters. Specifically in this image, the Law of Superposition allows scientists to determine which surface features pre- and postdate others, leading to a better understanding of the geological history of different regions of Mercury’s surface.
Or, in Sesame Street lingo, which comes first?
Also, C is for crater.
The MESSENGER spacecraft acquired this image on August 29, 2012.
Image credit: Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington. Click image for access to higher resolution versions.