Asteroid that lit up the sky in 2008 ‘once contained water’

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An asteroid that exploded in Earth’s atmosphere in 2008 was part of a much larger space rock that once held water, a new study reveals.

The asteroid, dubbed 2008 TC3, lit up the Sudan skies in October 2008 and dropped 600 meteorites, collectively known as Almahata Sitta.

After analyzing a fragment of Almahata Sitta, US researchers found evidence that it came from a large, water-rich parent asteroid about the size of a dwarf planet – anywhere from 400 to 1,100 miles (640 to 1,800 kilometers) in diameter.

Experts believe that the parent body was formed in the presence of water under intermediate temperatures and pressures, based on the unexpected presence of some type of amphibole crystal.

American scientists studied the composition of a small shard of a meteoroid to determine that it likely came from a previously unknown overhead asteroid. This false-color photomicrograph of the meteoroid sample shows the unexpected amphibole crystals identified in orange

American scientists studied the composition of a small shard of a meteoroid to determine that it likely came from a previously unknown overhead asteroid. This false-color photomicrograph of the meteoroid sample shows the unexpected amphibole crystals identified in orange

DIFFERENT TYPES OF SPACE ROCKS

A asteroid is a large piece of rock left over from collisions or the early solar system. Most are located between Mars and Jupiter in the main belt.

A comet is a rock covered with ice, methane and other compounds. Their orbits take them much further out of the solar system.

A meteor is what astronomers call a flash of light in the atmosphere when debris burns up.

This debris itself is known as one meteoroid. Most are so small that they are evaporated into the atmosphere.

When one of these meteoroid reaches Earth, it becomes one meteorite.

Meteors, meteoroids and meteorites normally come from asteroids and comets.

Amphiboles have hydroxyl groups in their structure and are considered stable only in environments where water can be incorporated into the structure.

“Our surprising result suggests the existence of a large, water-rich parent body,” said study author Vicky Hamilton of the Southwest Research Institute in Boulder, Colorado, USA.

Some of these meteorites are dominated by minerals that provide evidence of exposure to water at low temperatures and pressures.

The composition of other meteorites indicates heating in the absence of water.

‘Evidence for metamorphosis in the presence of water under intermediate conditions is virtually absent so far.’

Asteroids – and the meteors and meteorites that sometimes come out – are remnants of the formation of our solar system 4.6 billion years ago.

Most are in the main asteroid belt between the orbits of Mars and Jupiter, but collisions and other events have broken them up, throwing remains into the inner solar system.

Almahitta Sitta is named after the location in Sudan above which the space rock exploded in 2008.

The 9-ton asteroid with a diameter of 3 meters penetrated the Earth’s atmosphere and exploded in some 600 meteorites over Sudan.

Witnesses in the city of Wadi Halfa and at a railroad stop in the Nubian desert, known as “Station Six” or Almahata Sitta in Arabic, reported seeing a “missile-like fireball” in the sky.

Almahitta Sitta, a type of carbonaceous chondrite (CC) stone, has been preserved at the University of Khartoum, Sudan since its discovery in 2008.

Diamonds found in the Almahata Sitta meteorite (fragment, photo) come from a mysterious 'proto-planet' that was about 4.5 billion years ago, just a few million years after the birth of the sun

Diamonds found in the Almahata Sitta meteorite (fragment, photo) come from a mysterious ‘proto-planet’ that was about 4.5 billion years ago, just a few million years after the birth of the sun

CC meteorites are valuable because they record geological activity during the earliest stages of the solar system and provide insight into the history of their mother body.

CC meteorites also represent only a small fraction – 4.6 percent – of the meteorite fall.

‘We were assigned a 50 milligram AhS sample [Almahata Sitta] to study, ”Hamilton said.

‘We mounted and polished the small fragment and examined its composition with an infrared microscope.’

Spectral analysis identified a range of hydrated minerals, particularly tremolite, a rock-forming mineral and a member of the hydrated crystals group called amphibole.

“Essentially, this mineral forms under conditions that these meteorites were known to have never experienced before,” Hamilton said.

Animation of the 2008 TC3 asteroid that disintegrated over Sudan in 2008

‘[This] indicates intermediate temperatures and pressures and a prolonged period of watery change on a parent asteroid at least 400 miles in diameter and at most 1100 miles in diameter. ‘

Amphiboles are rare in CC meteorites because they have only previously been identified as a trace component in the Allende meteorite – the largest CC ever found on Earth, illuminating the Mexican sky in 1969.

“Almahata Sitta is an accidental source of information about early solar system materials not represented by CC meteorites in our collections,” Hamilton said.

The body from which the meteorite came will no longer exist, at least not in the form that was once the size of a dwarf planet.

But asteroid materials that arrived on the early Earth can differ significantly from what is represented by most meteorite collections.

The new study is published in Nature Astronomy.

WHAT IS THE ALMAHITTA SITTA?

The asteroid – first named 2008 TC3 and later named Almahata Sitta after the place in Sudan where witnesses saw it explode above Earth – was first spotted on Oct. 6 at 3:00 p.m. GMT.

It was only 20 hours away from the earthquake – although with an estimated diameter of only 5 meters, it would disintegrate in the atmosphere and pose no threat.

The 83-ton asteroid was tracked at an estimated speed of 27,739 mph until it disappeared in the planet’s shadow, then was observed exploding in a fireball as bright as a full moon.

The explosion 23 miles above Sudan at 2.45 GMT on October 7 – exactly where and when scientists predicted it – was seen by the crew of a KLM passenger jet as flashing over the horizon and was also spotted by several satellites.

Witnesses in the city of Wadi Halfa and at a railroad stop in the Nubian desert – ‘Station Six’ or Almahata Sitta in Arabic – reported seeing a ‘missile-like fireball’.

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