On Aug. 13, 2015 comet 67P/Churyumov-Gerasimenko achieved perihelion--its closest approach to the sun--accompanied by Europe's Rosetta spacecraft.
Rosetta arrived at the comet a year ago, and last Fall launched the Philae lander, which detected 16 different nitrogen- and carbon-rich organic compounds, four of which had never been found on a comet before.
The composition of comets, in particular their mix of organic compounds, is an intriguing subject of investigation, since one of the theories for the emergence of life on Earth involves the contribution of organic compounds by comets, asteroids, and protoplanets early in the formation of the solar system.
When Rosetta launched Philae in November 2014, the small spacecraft became the first ever to land on a comet. And though that landing did not go as planned--systems designed to pin down and hold fast to the comet failed--Philae was able to collect and transmit a useful load of data from near and on the comet's surface before its batteries wound down.
Since that encounter, and up to and beyond perihelion on August 13, Rosetta's mission has been to observe the effects of increasing solar radiation on comet Churyumov-Gerasimenko (C-G) over a year that brought it three times closer to the sun.