A new breed of comet at the heart of Hartley-2?

NASA researchers have claimed that they have discovered possibly a new breed of comet at the heart of Hartley-2.

Updated: May 18, 2011, 10:41 AM IST

Washington: NASA researchers have claimed that they have discovered possibly a new breed of comet at the heart of Hartley-2.
At the heart of every comet lies a remnant of the dawn of the solar system. Or is that remnants? Astronomers don`t know, but the answer would give them a clearer picture of exactly how comets were born eons ago at the birth of the Solar System.

Did thin tendrils of dust and ice get drawn slowly inward and pack themselves into a single, uniform mass? Or did a hodge-podge of mini-comets come together to form the core for a comet of substance?

For Hartley-2, the answer so far is neither.

"We haven`t seen a comet like this before. Hartley-2 could be the first of a new breed," said Michael Mumma of NASA`s Goddard Space Flight Center in Greenbelt, Md.

Data collected by Mumma`s team and detailed images of the comet taken by NASA`s EPOXI mission reveal that the Hartley-2`s core is not uniform.

"We have evidence of two different kinds of ice in the core, possibly three. But we can also see that the comet`s overall composition is very consistent. So, something subtle is happening. We`re not sure what that is," said Mumma.

The researchers observed Hartley-2 six times during the summer, fall and winter of 2010, both before and after the EPOXI mission`s Deep Impact spacecraft had its November rendezvous with the comet.

Using telescopes perched high in the mountains of Hawaii and Chile, they studied the comet`s coma -- the aura of gas, dust and ice particles that surround the core.

Mumma and colleagues paid close attention to the levels of water and seven other molecules that evaporate easily. The molecules remain frozen either on or below the core`s surface until the warming rays of the sun vaporize them; then, they are swept into the coma.

The team discovered something very strange: "The amount of water changed dramatically night by night and even within a single night-in some cases, doubling in that time," said Mumma. But, in truth, Hartley-2 isn`t the only comet to get caught being fickle.

What surprised the researchers was this: as the amount of water went up, so did the amounts of the other gases. And as the amount of water went down, the others did, too.

"This is the first time anyone has seen an entire suite of these gases change in the same way at the same time," said Mumma.

The study is detailed in Astrophysical Journal Letters.