Monday December 10, 2018

NASA’s OSIRIS-REx Spacecraft begins 2-week search for enigmatic class of near-Earth objects known as Earth-Trojan asteroids

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Aerial View of NASA. Wikimedia
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Washington, Feb 10, 2017: NASA said its OSIRIS-REx spacecraft has started a two-week search for an enigmatic class of near-Earth objects known as Earth-Trojan asteroids.

The mission, currently on a two-year outbound journey to the asteroid Bennu, will spend almost two weeks searching for evidence of these small bodies, the US space agency said on Thursday.

Although scientists have discovered thousands of Trojan asteroids accompanying other planets, only one Earth-Trojan has been identified to date, asteroid 2010 TK7.

Scientists predict that there should be more Trojans sharing Earth’s orbit but they are difficult to detect from Earth as they appear near the sun on the Earth’s horizon.

“So this search gives us a unique opportunity to explore the primordial building blocks of Earth,” said principal investigator Dante Lauretta of the University of Arizona, Tucson.

Trojan asteroids are trapped in stable gravity wells, called Lagrange points, which precede or follow a planet.

Launched on September 8, 2016, OSIRIS-REx is currently travelling through Earth’s fourth Lagrange point, which is located 60 degrees ahead in Earth’s orbit around the sun, about 150 million km from Earth.

The mission team will use this opportunity to take multiple images of the area with the spacecraft’s MapCam camera in the hope of identifying Earth-Trojan asteroids in the region.

“Because the Earth’s fourth Lagrange point is relatively stable, it is possible that remnants of the material that built Earth are trapped within it,” Lauretta said.

The operations involved in searching for Earth-Trojan asteroids closely resemble those required to search for natural satellites and other potential hazards around Bennu when the spacecraft approaches its target in 2018, NASA said. (IANS)

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Wintertime Ice Growth in Arctic Sea Slows Long-Term Decline: NASA

The switch will happen once the sea ice is less than 1.6 feet thick at the beginning of winter, or its concentration

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Wintertime ice growth in Arctic sea slows long-term decline: NASA. Flcikr

While sea ice in the Arctic continues to be on the decline, a new research from the US Space agency NASA suggests that it is regrowing at faster rates during the winter than it was a few decades ago.

The findings showed that since 1958, the Arctic sea ice cover has lost on average around two-thirds of its thickness and now 70 per cent of the sea ice cap is made of seasonal ice, or ice that forms and melts within a single year.

But at the same time, that sea ice is vanishing quicker than it has ever been observed in the satellite record, it is also thickening at a faster rate during winter.

This increase in growth rate might last for decades, explained the researchers, in the paper to be published in the journal Geophysical Research Letters.

However, this does not mean that the ice cover is recovering, though. Just delaying its demise.

“This increase in the amount of sea ice growing in winter doesn’t overcome the large increase in melting we’ve observed in recent decades,” said lead author Alek Petty, a sea ice scientist at NASA’s Goddard Space Flight Center in Maryland.

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However, this does not mean that the ice cover is recovering, though. Just delaying its demise. Flickr

“Overall, thickness is decreasing. Arctic sea ice is still very much in decline across all seasons and is projected to continue its decline over the coming decades,” she added.

To explore sea ice growth variability across the Arctic, the team used climate models and observations of sea ice thickness from the European Space Agency’s CryoSat-2 satellite.

They found that in the 1980s, when Arctic sea ice was on average 6.6 feet thick in October, about 3.3 extra feet of ice would form over the winter.

This rate of growth may continue to increase, and in the coming decades, we could also have an ice pack that would on average be only around 3.3 feet thick in October, but could experience up to five feet of ice growth over the winter.

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However, by the middle of the century, the strong increases in atmospheric and oceanic temperatures will outweigh the mechanism that allows ice to regrow faster, and the Arctic sea ice cover will decline further, Petty said.

The switch will happen once the sea ice is less than 1.6 feet thick at the beginning of winter, or its concentration — the percentage of an area that is covered in sea ice — is less than 50 per cent, she noted. (IANS)