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

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Dr. Chaitanya Giri, Postdoctoral Research Scientist, Max Planck Institute for Solar System Research
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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)

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Researchers Have Successfully Created Artificial Placenta

Initial tests have already shown that the artificial placenta on the chip does in fact behave in a similar way to a natural placenta: small molecules are allowed to pass through, while large ones are held back, the researchers noted.

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Artificial placenta created in lab using 3D printing. Flickr
Artificial placenta created in lab using 3D printing. Flickr

Using a high-resolution 3D printing process, Austrian researchers have succeeded in creating an artificial placenta barrier on a chip, a development that can be used to investigate important aspects of nutrient transport from the mother to the foetus.

The placenta ensures the exchange of important substances between the mother and her unborn child, whilst simultaneously blocking other substances from passing through.

“The transport of substances through biological membranes plays an important role in various areas of medicine,” said Aleksandr Ovsianikov, professor at the TU Wien university in Vienna.

“These include the blood-brain barrier, ingestion of food in the stomach and intestine, and also the placenta.”

This can help provide clarity on how the exchange of glucose between mother and child takes place. Wikimedia Commons
This can help provide clarity on how the exchange of glucose between mother and child takes place. Wikimedia Commons

Studies have shown that diseases such as diabetes and high blood pressure in the mother can affect the transport of substances to the foetus. Until now however, it has been almost impossible to investigate the way in which the many parameters involved interact in such cases.

Using the 3D printing made it possible to produce customised hydrogel membranes directly within microfluidic chips, which are then populated with placenta cells.

This can help provide clarity on how the exchange of glucose between mother and child takes place, the researchers said.

The novel chip consists of two areas — one represents the foetus, the other the mother. Using a specially developed femtosecond laser-based 3D printing process helped produce a partition between them — the artificial placenta membrane.

The high-resolution 3D printing involved a hydrogel with good biocompatibility.

Also Read: Obesity During Pregnancy May up Kid’s Risk of Epilepsy

“Based on the model of the natural placenta, we produce a surface with small, curved villi. The placenta cells can then colonise it, creating a barrier very similar to the natural placenta,” Ovsianikov explained.

Initial tests have already shown that the artificial placenta on the chip does in fact behave in a similar way to a natural placenta: small molecules are allowed to pass through, while large ones are held back, the researchers noted. (IANS)