An asteroid that exploded in Earth’s atmosphere in 2008 was part of a much larger space rock that once contained water, a new study shows.
The asteroid, named 2008 TC3, illuminated Sudan’s sky in October 2008 and flooded the earth with 600 meteorites, collectively called Almahata Sitta.
After analyzing a fragment of Almahata Sitta, US researchers found evidence that it came from a large, watery 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 mother body is formed in the presence of water under intermediate temperatures and pressures, based on the unexpected presence of a type of amphibole crystal.
U.S. researchers examined the composition of a small shard of a meteoroid to determine that it probably originated from a previously unknown parent asteroid. This false color photomicrograph of the meteoroid sample shows the unexpected amphibole crystals identified in orange
DIFFERENT TYPES OF SPACE ROCKS
One asteroid is a large rock rock left from collisions or the early solar system. Most are located between Mars and Jupiter in the main belt.
ONE comet is a rock covered with ice, methane and other compounds. Their orbits lead them much further out of the solar system.
ONE meteor is what astronomers call a flash of light in the atmosphere when waste burns up.
This waste in itself is known as one meteoroid. Most are so small that they evaporate into the atmosphere.
If any of this meteoroid reaches Earth, it is called one meteorite.
Meteors, meteoroids and meteorites usually originate from asteroids and comets.
Amphiboles have hydroxyl groups in their structure and are only considered to be stable in environments where water can be incorporated into the structure.
‘Our surprising result suggests the existence of a large, watery 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 warming in the absence of water.
‘Evidence of metamorphism in the presence of water under intermediate conditions has so far been absent.’
Asteroids – and the meteors and meteorites that sometimes come from them – are remnants of the formation of our solar system 4.6 billion years ago.
Most live in the main asteroid belt between Mars and Jupiter’s orbits, but collisions and other events have broken them up and pushed remnants into the inner solar system.
Almahitta Sitta is named after its location in Sudan, over which the space rock exploded in 2008.
The 9-ton, 13-foot diameter asteroid entered Earth’s atmosphere and exploded in some 600 meteorites over Sudan.
Witnesses in the town of Wadi Halfa and at a railway stop in the Nubian desert, known as ‘Station Six’ or Almahata Sitta in Arabic, reported that they had seen a ‘rocket-like fireball’ in the sky.
Almahitta Sitta, a type of carbonaceous chondrite (CC) stone, has been stored at the University of Khartoum, Sudan since its discovery in 2008.
Diamonds found in the Almahata Sitta meteorite (fragment, pictured) 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 the geological activity in the earliest stages of the solar system and provide insight into the stories of their parent bodies.
CC meteorites also represent only a small proportion – 4.6 percent – of meteorite falls.
‘We were given a 50 milligram sample of AhS [Almahata Sitta] to study, ‘said Hamilton.
‘We mounted and polished the small shard and used an infrared microscope to examine its composition.’
Spectral analysis identified a number of hydrated minerals, especially tremolite, a rock-forming mineral, and a member of the group of hydrated crystals called amphibole.
‘Essentially, this mineral is formed under conditions that these meteorites were not previously known to have experienced,’ Hamilton said.
Animation of the TC3 asteroid 2008 that broke out over Sudan in 2008
”[This] points to intermediate temperatures and pressures and an extended period of aqueous change on a parent asteroid that is at least 400 and up to 1,100 miles in diameter. ‘
Amphiboles are rare in CC meteorites, having only previously been identified as a trace component in the Allende meteorite – the largest CC ever found on Earth, which illuminated the Mexican sky in 1969.
‘Almahata Sitta is a serendipitous 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 its once dwarf planetary form.
However, asteroid materials arriving in early Earth may have differed markedly from what is represented by most meteorite collections.
The new study is published in Nature Astronomy.
WHAT IS ALMAHITTA SIT?
The asteroid – first marked 2008 TC3 and later named Almahata Sitta after the place in Sudan where witnesses saw it explode over Earth – was first seen on October 6 at. 15 GMT.
It was only 20 hours away from ground attack – but with a diameter estimated at only 16 feet, it was bound to break up in the atmosphere and posed no threat.
The 83-ton asteroid was tracked, estimated at 27,739 mph, until it disappeared into the planet’s shadow and was then observed as it exploded in a fireball as bright as a full moon.
The blast 23 miles over Sudan at. 14.45 GMT on October 7 – exactly where and when scientists had predicted – was seen by the crew of a KLM passenger plane flashing on the horizon and was also seen by various satellites.
Witnesses in the town of Wadi Halfa and at a railway stop in the Nubian desert – ‘Station Six’ or Almahata Sitta in Arabic – reported that they had seen a ‘rocket-like fireball’.