The skies of Mars just got a little more crowded. On September 21st, 2014 NASA's Mars Atmosphere and Volatile Evolution Mission (MAVEN) fired its engines for some 33 minutes in order to swing into a safe orbit. And a few days later, early on Sept 24th, India's Space Research Organization (ISRO) made history by joining the likes of the US, the former Soviet Union, and Europe, in successfully placing a spacecraft into martian orbit - their Mars Orbiter, or Mangalyaan ("Mars-craft") mission.

The Indian accomplishment is hugely impressive. Even if Mangalyaan is primarily a test bed for a variety of spacecraft engineering designs - carrying a handful of scientific instruments - to get anything to Mars in one piece is quite something. The history of efforts to explore the 4th planet from the Sun is littered with disappointments, and quite a few unintentional craters. Only about 43% of Mars missions have had any kind of success. Little wonder that the men and women of ISRO were very, very happy.

Among the Lyman-Alpha Photometer, Methane Sensor, Quadrupole mass analyzer, and Thermal Infrared Imaging Spectrometer instruments is a plain old camera, and it's sent back one of the first released images from this mission - shown here.

The surface of Mars imaged by Mangalyaan from about 7,300 km (ISRO)

At the same time, NASA's MAVEN is firing up its own scientific instruments for a highly detailed study of the Martian atmosphere. Although it's presently in an elliptical orbit with a 35 hour period (not yet in its final science orbit with a 4.5 hour period) MAVEN's array of detectors are getting to work.

On board are a Solar Wind Ion Analyzer, a Solar Wind Electron Analyzer, a Solar Energetic Particle detector, a SupraThermal and Thermal Ion Composition instrument, a Langmuir Probe and Waves device (looking at fast plasma oscillations), a Magnetometer, an Extreme Ultraviolet Monitor, a Neutral Gas and Ion Mass Spectrometer, and an Imaging Ultraviolet Spectrograph. A principle goal is to learn about how Mars's atmosphere is being lost today, and to try to use this data to extrapolate back into martian history to evaluate what the atmospheric evolution may have been over millions and billions of years. During its primary mission MAVEN will also 'dip' to within 77 miles of Mars to probe its upper atmosphere in more detail.

Interestingly, MAVEN does not carry a methane detector - methane being a potential signature of biological activity today - but Mangalyaan does. Nor does MAVEN have a conventional visible light camera. But it does have that ultraviolet imaging spectrograph, and so naturally that's provided one of the first images sent back - a mere 8 hours after arrival.

Images of Mars in 3 ultraviolet bands(Courtesy Laboratory for Atmospheric and Space Physics /University of Colorado and NASA).

What are we looking at? Blue colors represent far-ultraviolet light from the Sun that's getting scattered by atomic hydrogen which exists in a great halo-like cloud above Mars. Green is the ultraviolet scattering due mostly to oxygen. Red is mid-ultraviolet light bouncing off the surface of Mars - showing a brighter region at the southern pole, either ice or cloud.

You may wonder where hydrogen and oxygen are coming from if the thin martian atmosphere is mostly carbon dioxide? It's from the dissociation of water and carbon dioxide molecules at high altitudes

The blue glow in these images is therefore part of the very thing that MAVEN went to Mars to study - hydrogen being lost to space, hydrogen that used to be in water and which therefore represents the ongoing drying out of this dusty world.