Monday October 22, 2018
Home Uncategorized Why comets ap...

Why comets appear black? Indian-led scientists’ group finally finds answer

0
//
102
Indian
Dr. Chaitanya Giri, Postdoctoral Research Scientist, Max Planck Institute for Solar System Research
Republish
Reprint

Bengaluru: A study by an international team from Europe and the US led by an Indian planetary scientist has resolved one of the mysteries that baffled astronomers.

Astronomical studies have shown that several small bodies – Centaurs and Trans-Neptunian Objects (TNOs) – in the outer solar system are having surfaces that are extremely dark but the origin of this color had remained unclear.

Centaurs estimated to number around 44,000 are minor planets with diameters larger than one kilometer. And TNOs are similar objects at a distance farther than Neptune, the most distant planet in the solar system.

Now, in a report published in the International Journal of Astrobiology, Dr. Chaitanya Giri, who led the research from the Max Planck Institute for Solar System Research in Germany, and co-workers claim to have found why these objects appear dark.

They say they have obtained experimental evidence that the darkness of these objects is due to presence on their surfaces of highly ‘carbonized’ organic material analogous to ‘Titan tholin’ — a substance first synthesized in the late 1970s in the laboratory of Carl Sagan and another Indian scientist Bishun Khare at Cornell University to simulate the atmosphere of Saturn’s moon ‘Titan’.

“We investigated the chemical structure and composition of ‘Titan tholin’ using multiple analytical techniques such as laser desorption, mass spectrometry, Raman spectroscopy, and field-emission scanning electron microscopy,” Giri told IANS in an email.

“The investigation led to the discovery of novel graphitic structural components within the larger macromolecular structure of Titan tholin,” he said.

“Like the dark appearance of coal, our research indicates that the graphite within the Titan tholin-like material on Centaurs and TNOs contributes to their extreme darkness.”

According to Giri, since Centaurs and TNOs are progenitors of comets, “the darkness of the comet’s surface can also be attributed to similar material.”

For instance comet “67P/Churyumov-Gerasimenko”, which was visited by Europe’s Rosetta space mission in 2014, “was extremely dark,” said Giri, who was a co-investigator on the mission.

Giri, who is currently with Japan’s Earth Life Science Institute at the Tokyo Institute of Technology, says the findings of this research will have far-reaching implications.

“For astronomers and planetary scientists, the prospect of complex organic material present on several objects in our Solar System is striking,” he said.

Astronomers might further use “Titan tholin” to study the surfaces of exoplanets (that are planets beyond our solar system) and planetary scientists could probe into the role of tholin-like material in shaping up organic-rich atmosphere and geology of several solar system objects.

“Chemists could further explore the exotic conformations in which ultra-complex organics exist in the universe and biologists would further probe whether such organics play any role in the origin of life on Earth,” he added.

Giri noted that in the past few years, interest in the small Solar System bodies had been on an ascent.

“Besides Europe’s Rosetta mission, NASA’s Dawn mission to dwarf planet Ceres and the New Horizons mission to dwarf planet Pluto all have given us glimpses to our yet unexplored and enormously diverse Solar System.”

Giri said the “Titan tholin” for his study was synthesized at the NASA Ames Research Center while chemical investigations were carried out at the Max Planck Institute for Solar System Research, NASA Goddard Space Flight Center, and at the Universities of Maryland (US), Nice (France), and Goettingen (Germany). (IANS)(Photo: chaitanyagiri.com)

Click here for reuse options!
Copyright 2016 NewsGram

Next Story

Invasive Species May Not Be All Bad: Scientists

An active debate among biologists about the role of invasive species in a changing world is going on

0
Invasive Species
The invasive European green crab is tearing down ecosystems in Newfoundland and building them up on Cape Cod. VOA

Off the shores of Newfoundland, Canada, an ecosystem is unraveling at the hands (or pincers) of an invasive crab.

Some 1,500 kilometers (930 miles) to the south, the same invasive crab — the European green crab — is helping New England marshes rebuild.

Both cases are featured in a new study that shows how the impacts of these alien invaders are not always straightforward.

Around the world, invasive species are a major threat to many coastal ecosystems and the benefits they provide, from food to clean water. Attitudes among scientists are evolving, however, as more research demonstrates that they occasionally carry a hidden upside.

“It’s complicated,” said Christina Simkanin, a biologist at the Smithsonian Environmental Research Center, “which isn’t a super-satisfying answer if you want a direct, should we keep it or should we not? But it’s the reality.”

Simkanin co-authored a new study showing that on the whole, coastal ecosystems store more carbon when they are overrun by invasive species.

Good news, crab news

Take the contradictory case of the European green crab. These invaders were first spotted in Newfoundland in 2007. Since then, they have devastated eelgrass habitats, digging up native vegetation as they burrow for shelter or dig for prey. Eelgrass is down 50 percent in places the crabs have moved into. Some sites have suffered total collapse.

That’s been devastating for fish that spend their juvenile days among the seagrass. Where the invasive crabs have moved in, the total weight of fish is down tenfold.

The loss of eelgrass also means these underwater meadows soak up less planet-warming carbon dioxide from the atmosphere.

In Cape Cod, Massachusetts, the same crab is having the opposite impact.

Off the coast of New England, fishermen have caught too many striped bass and blue crabs. These species used to keep native crab populations in check. Without predators to hold them back, native crabs are devouring the marshes.

But the invasive European green crab pushes native crabs out of their burrows. Under pressure from the invader, native crabs are eating less marsh grass. Marshes are recovering, and their carbon storage capacity is growing with them.

Invasive species
In this May 8, 2016 photo, eelgrass grows in sediment at Lowell’s Cove in Harpswell, Maine. VOA

Carbon repositories

Simkanin and colleagues compiled these studies and more than 100 others to see whether the net impact on carbon storage has been positive or negative.

They found that the ones overtaken by invasive species held about 40 percent more carbon than intact habitats.

They were taken by surprise, she said, because “non-native species are thought of as being negative so often. And they do have detrimental impacts. But in this case, they seem to be storing carbon quicker.”

At the Smithsonian Environmental Research Center where she works, the invasive reed Phragmites has been steadily overtaking a marsh scientists are studying.

Phragmites grows much taller, denser and with deeper roots than the native marsh grass it overruns.

But those same traits that make it a powerful invader also mean it stores more carbon than native species.

“Phragmites has been referred to as a Jekyll and Hyde species,” she said.

Not all invaded ecosystems stored more carbon. Invaded seagrass habitats generally lost carbon, and mangroves were basically unchanged. But on balance, gains from marsh invaders outweighed the others.

Invasive species
Phragmites plants growing on Staten Island draft in a breeze in the Oakwood Beach neighborhood of Staten Island. VOA

Not a lot of generalities

To be clear, Simkanin said the study is not suggesting it’s always better to let the invaders take over; but, it reflects an active debate among biologists about the role of invasive species in a changing world.

“One of the difficult things in the field of invasion biology is, there aren’t a lot of generalities,” said Brown University conservation biologist Dov Sax, who was not involved with the research. “There’s a lot of nuance.”

The prevailing view among biologists is that non-native species should be presumed to be destructive unless proven otherwise.

When 19 biologists wrote an article in 2011 challenging that view, titled, “Don’t judge species on their origins,” it drew a forceful rebuke from 141 other experts.

Sax said the argument is likely to become more complicated in the future.

Also Read: Climate Change Not A Hoax: Trump

“In a changing world, with a rapidly changing climate, we do expect there to be lots of cases where natives will no longer be as successful in a region. And some of the non-natives might actually step in and play some of those ecosystem services roles that we might want,” he said.

“In that context, what do we do? I definitely don’t have all the answers.” (VOA)