Two missions to Mars this week.

This week two orbiters have begun circling the red planet. One is the NASA's Maven orbiter and the other is from India's Space Research Organization (ISRO) and is called the Mangalyaan which is sanscrit for "Mars" "Craft".
Both craft have successfully entered high altitude elliptical orbits around Mars.
The Nasa mission is designed to study why Mars' once thick, dense atmosphere that was capable of sustaining liquid water vanished. The ISRO mission is designed to map the topology of the Mars terrain.
Both are useful space missions that will hopefully lead to greater understanding of the cosmos.
You can read more about Maven here, here and here. You can read more about Mangalyaan here, here, and here.