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Hubble captures farthest active inbound comet

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nasa's hubble space telescope

Washington, Sep 29: NASA’s Hubble Space Telescope has captured the farthest active inbound comet ever seen, at a whopping distance of 1.5 billion miles from the Sun.

Slightly warmed by the remote Sun, it has already begun to develop an 80,000-mile-wide fuzzy cloud of dust, called a coma, enveloping a tiny, solid nucleus of frozen gas and dust, according to a study published in the Astrophysical Journal Letters.

These observations represent the earliest signs of activity ever seen from a comet entering the solar system’s planetary zone for the first time.

The comet, called C/2017 K2 (PANSTARRS) or “K2”, has been travelling for millions of years from its home in the frigid outer reaches of the solar system, where the temperature is about minus 226 degrees Celsius.

Comets are the icy leftovers from the formation of the solar system 4.6 billion years ago and therefore pristine in icy composition.

“K2 is so far from the Sun and so cold, we know for sure that the activity — all the fuzzy stuff making it look like a comet — is not produced, as in other comets, by the evaporation of water ice,” said lead researcher David Jewitt of the University of California, Los Angeles.

“Instead, we think the activity is due to the sublimation (a solid changing directly into a gas) of super-volatiles as K2 makes its maiden entry into the solar system’s planetary zone. That’s why it’s special. This comet is so far away and so incredibly cold that water ice there is frozen like a rock,” Jewitt said.

Based on the Hubble observations of K2’s coma, Jewitt suggests that sunlight is heating frozen volatile gases – such as oxygen, nitrogen, carbon dioxide, and carbon monoxide – that coat the comet’s frigid surface.

These icy volatiles lift off from the comet and release dust, forming the coma. Past studies of the composition of comets near the Sun have revealed the same mixture of volatile ices.

“I think these volatiles are spread all through K2, and in the beginning billions of years ago, they were probably all through every comet presently in the Oort Cloud,” Jewitt said.

“But the volatiles on the surface are the ones that absorb the heat from the Sun, so, in a sense, the comet is shedding its outer skin. Most comets are discovered much closer to the Sun, near Jupiter’s orbit, so by the time we see them, these surface volatiles have already been baked off. That’s why I think K2 is the most primitive comet we’ve seen,” Jewitt added.(IANS)

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Comets: The harbingers of life on earth?

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Rosetta

 

By K.S.Jayaraman

Bengaluru: Did a comet strike jump-start life on Earth? The findings of the European Space Agency’s Rosetta Mission tend to suggest this possibility.

An instrument on board the Philae Lander of Rosetta Mission has identified 16 organic molecules on the surface of a comet that are potentially “prebiotic”, or necessary for life, the mission scientists have reported in a recent issue of the journal Science.

“These are the first organic molecules to be ever reported directly, from in-situ analyses, from the surface of a comet,” Chaitanya Giri, a co-investigator of Cometary Sampling and Composition Experiment (COSAC) of the Rosetta Mission and one of the authors, told IANS.

On November 12, 2014, Philae Lander became the first space probe to soft land on the surface of a comet called 67P/Churyumov-Gerasimenko. Besides COSAC, Philae carried several scientific experiments on board, with each trying to decipher the nature of the comet.

COSAC – which is a gas chromatography-mass spectrometer – aimed to study the surface ‘organic’ chemical composition of the comet, said Giri, a post-doctoral research scientist in the Department of Planets and Comets at the Max Planck Institute for Solar System Research (MPS) in Gottingen, Germany.

According to the report, the Philae Lander bounced off the comet’s surface multiple times after the touchdown before coming to rest. The dust cloud kicked up from the bounces entered the COSAC instrument, which analysed the dust. “The entire COSAC team studied the mass spectra data generated by it,” Giri said.

The COSAC team, led by Fred Goesmann, involved scientists from France, Germany, Ireland, the Netherlands, Spain, Switzerland and the United States. Giri, the only Indian on board, has been part of the team for the past five years in various capacities, beginning as a trainee doctoral student.

According to the Science report, as many as 16 molecules were identified by the experiment. Twelve of these had been reported earlier from remote ground-based telescopes and fly-by missions whereas COSAC has reported four novel molecules that have never been reported earlier, Giri said.

These new molecules are acetamide, methyl isocyanate, propionaldehyde and acetone. Other re-reported molecules include hydrogen cyanide, formamide and glycolaldehyde.

“All these molecules are of great significance for triggering pre-biotic chemistry – the precursor processes towards the formation of life,” Giri said. These are the same molecules that are known to be the building blocks for the origin of life on Earth and are major constituents of known molecular biological processes, he said.

For instance, Glycolaldehyde is known to play a crucial role in the prebiotic synthesis of sugars. Hydrogen cyanide is a known and important precursor for synthesis of amino acids and nucleobases. Formamide and acetamide are known to play a crucial act in the formation of nucleobases and phosphorylation of nucleosides to nucleotides. Within their chemical structure they also contain the so-called “CONH” bond that is the only known way to polymerize amino acids into peptides and further into proteins.

“For centuries, comets have been regarded as omens of destruction,” Giri said. “Our findings have revolutionized human perception of comets. The COSAC-reported potentially prebiotic molecules now point to the likely role of comets as harbingers of life on Earth.”

However, many important questions yet remain unanswered and further exploration of comets and other small bodies is indicated, he added.

“Rosetta is an icon of international co-operation, public support and state-of-the-art science and technology. Such missions are crucial prerequisites for human advancement in outer space. The knowledge gained through Rosetta urges us to explore even further,” he said.

(IANS)