Rosetta reveals a lot about comet even as Philae lander is MIA


Researchers over at the University of Maryland (UMD) have revealed never-before seen details of a comet using the European Space Agency’s Rosetta spacecraft all the while when the Philae lander, which touch down on the surface of 67P/Churyumov-Gerasimenko (C-G), is still missing in action.

The team comprising of Michael A’Hearn, distinguished university professor emeritus of astronomy at UMD, and astronomer Dennis Bodewits co-authored three papers revealing the C-G and its details to a great depth. The researchers said that the study has helped scientists better understand comets in terms of how they are formed, how their surfaces evolve over time and how to potentially predict their lifespans.

“We are trying to see how a comet evolves over time, and also through the course of its orbit. Gaining this detailed time series is what distinguishes Rosetta from other missions,” said Michael A’Hearn.

The duo has co-authored three of the papers as members of the team for Rosetta’s Optical, Spectroscopic and Infrared Remote Imaging System (OSIRIS), one of them based on OSIRIS images to analyse the structure of C-G.

The OSIRIS imager packs two cameras, each with its own set of specialized filters – the narrow angle camera is designed to image the surface of the comet’s nucleus and the wide angle camera focuses on the cloud of gas and dust around it.

From the looks of it C-G looks roughly like a rubber duck with two lobes connected by a thin “neck”. The team found that the majority of outgassing activity from the comet is occurring at the neck, where the OSIRIS cameras have consistently seen jets of gas and debris.

The second paper describes the surface of the portion of C-G that is currently visible to Rosetta. This “northern” region is divided into 19 distinct regions, all named for ancient Egyptian deities in keeping with the nomenclature of the mission.

A third paper combines data from OSIRIS and another instrument, the Grain Impact Analyser and Dust Accumulator (GIADA). This study looks at C-G’s coma – the thick cloud of dust and gas that envelops the nucleus. Comets have very little gravity, dust and gas flow freely into the space.

“We were surprised to find a cloud of particles orbiting the comet that are large and heavy enough to defy the sun’s radiation pressure,” Bodewits said.

The comet will be most active when it reaches perihelion or the single point in C-G’s orbit that is the closest and most intensely affected by solar radiation.

It will reach this point Aug 13, 2015 after which it will head away from the Sun once again.