For years, scientists have been puzzled by DNA-sized diamonds in meteorites on Earth. New research suggests that these diamonds spring from violent cosmic collisions, which may help scientists unravel mysteries surrounding exploding stars -- the supernova birthplaces of ancient materials that predate our solar system.
Although diamonds are rare on Earth, scientists believe that minuscule "nanodiamonds" are common in space. Researchers have been trying to decipher the origin of these mysterious minerals for decades.
"The transformation is quite astonishing," said Nigel Marks, a materials scientist at Curtin University in Perth, Australia, and coauthor of the research paper. "I never would have imagined this was possible."
Marks completed computer simulations of space dust collisions and found that diamond formation didn't require blistering temperatures or crushing pressures. Instead, diamonds formed when carbon-containing dust grains smashed together at speeds exceeding 10,000 miles per hour.
Within the original grains, soccer-ball-shaped carbon molecules known as spherical fullerenes enclosed one another like Russian nesting dolls. Together, these concentric molecules compose layered carbon "onions."
When the carbon onions slammed into each other, the molecules flattened, squeezed and linked together, rearranging themselves into hexagonal shapes indicative of diamond structure.
If they collided at high enough speeds, then the carbon onions were destroyed. And if the particles weren't moving fast enough, then the carbon onions did not complete the transition to diamonds. The researchers found that the narrow speed range required for nanodiamond formation is common in space.
"There's a huge message embedded in the nanodiamond," said Marks. "[Researchers] just couldn't figure out what it was."
Forms of elements such as gaseous xenon with different amounts of neutrons have been found inside meteorite nanodiamonds. Called isotopes, these variants of the same elements convey information about exploding stars from earlier in the universe's history. Different ratios of isotopes are produced in different nuclear reactions, giving scientists clues as to what types of dying stars gave birth to these isotopes.
According to Marks and his team, xenon is likely incorporated into carbon onions before they collide and produce nanodiamonds. By better understanding where these embedded isotopes originate, scientists can glean new information about the death of stars and the origins of our solar system.
Several competing theories, however, suggest nanodiamonds were formed differently than Marks' research indicates. For instance, some scientists think that shock waves from exploding stars may have created nanodiamonds. Intense pressure and heat from the shock wave could also have led to the implantation of noble gases like xenon.
But all theories put forth so far have been hampered by limited experimental evidence. Because nanodiamonds are so small, it's been extremely difficult to look at them individually.
To help resolve this issue, Marks and his colleagues hope to translate their simulations into lab experiments in the coming months. By creating nanodiamonds on Earth, the research team could produce large enough samples to analyze.
The NASA Chandra X-ray Observatory image of a supernova SNR 0540-69.3 at the top of the page shows two aspects of the enormous 'diamond-creating' power released when a massive star explodes. An implosion crushed material into an extremely dense (10 miles in diameter) neutron star, triggering an explosion that sent a shock wave rumbling through space at speeds in excess of 5 million mph.
The image reveals a central intense white blaze of high-energy particles about 3 light years across created by the rapidly rotating neutron star, or pulsar. Surrounding the white blaze is a shell of hot gas 40 light years in diameter that marks the outward progress of the supernova shock wave. Whirling around 20 times a second, the pulsar is generating power at a rate equivalent to 30,000 Suns.