Updated at 1:14 p.m. Thursday
Earthlings are in for a treat Monday as Mercury makes a relatively rare transit of the sun.
The solar system's smallest, innermost planet will resemble a black round dot as it passes in front of our big, bright star. The last time Mercury crossed directly between the Earth and sun was in 2006, and it won't happen again until 2019 — and then, until 2032. NASA says the event occurs only about 13 times a century.
Louis Mayo, program manager at NASA's Goddard Space Flight Center in Greenbelt, Maryland, considers it "a big deal."