Oddball comet Hartley 2 puzzles astronomers trying to crack secrets of solar system

Scientists who analyzed the images of Comet Hartley 2, which was collected by the Deep Impact spacecraft in a comet flyby last year, are puzzled over some quirky features of the little comet.

It has been found that Comet Hartley 2 spews out more material than a comet just under a mile wide is expected to, space.com has reported. While comets usually rotate slowly in one direction, Hartley 2 spins rapidly as it tumbles.

Also, Hartley 2 contains an inexplicable amount of carbon dioxide, causing it to burp and even hock ice loogies into space, the report said.

Scientists are puzzled over Hartley 2's strange features and ill-mannered water-spouting. And they are forced to revisit some theories regarding the solar system's formation.

The unusual comet is raising questions over some longtime assumptions by scientists on how comets formed in the early solar system, said the scientists involved in the new study.

Comets are essentially balls of ice, gas, and dust that and they have been presumably in existence for billions of years, since the time the planets in the solar system came into being. Scientists have always believed the study of comets can give vital clues to the formation of the solar system.

Hartley 2 has thrown them off track. Our assumptions of what drives a typical comet's activity, as well as what the composition of the primordial disk was and how much mixing occurred in the disk, have been turned upside down. We need to re-evaluate our theories, said Lori Feaga, a University of Maryland planetary scientist, according to space.com.

For scientists, understanding what drives comets' activity is very important as they delve into the mysteries of the solar system. Water-spewing comet Hartley 2 has puzzled the scientists in a couple of ways. First, it is unclear why the comet has so much CO2 in it.
Feaga, who works on NASA's Extrasolar Planet Observation and Deep Impact Extended Investigation (EPOXI) mission, says dry ice is what's driving the comet's hyperactivity. It drives icy particles such as silicates, dust grains and water-ice out of the interior of the comet.

When the dry ice in the interior heats up, it changes to a gas, which is much less dense. As it expands, it creates an explosive force that pulls out other things with it as it tunnels through the nucleus to get out.

But Hartley 2 spews twice as much from one of its bulbous sides than from the other, Feaga says.

And that leads to the second confusion. If one end of comet Hartley 2 spews out double the amount of dry ice than the other, it could mean that the two ends could have been formed in separate places in the early solar system, according to the scientists. These ends could have collided at a later point and got stuck.

In the solar system during its formation, there was a proto-planetary disk that was like a large Frisbee of rotating material ... The higher-density material like iron was closer to the sun, and the lower-density materials like ices were further out. So depending on the distance from the sun, we have this assumption for what existed there, Feaga explained.