July 18, 2014
Diamond Compression Experiment Could Provide Insight Into Gas Giant Cores
redOrbit Staff & Wire Reports - Your Universe Online
Using the largest laser in the world, scientists working at the Lawrence Livermore National Laboratory (LLNL) successfully compressed diamond to core pressures comparable to those found on Jupiter and Saturn, according to research appearing in the journal Nature.
Researchers from LLNL, the University of California, Berkeley and Princeton University used lasers housed at the laboratory’s National Ignition Facility (NIF) to squeeze samples of the hardest material in existence to 50 million times our planet’s atmospheric pressure – 14 times that found at the center of the Earth, BBC News science reporter James Morgan explained on Wednesday.
The authors used 176 of the NIF’s 192 lasers to produce a pressure wave that compressed the material for an extremely short period of time. While the compressed diamonds vaporized in less than 10 billionths of a second, SFGate.com reporter David Perlman said the experiments could shed new light on the behavior of the carbon-rich planets in our solar system, as well as the millions of exoplanets and stars that exist beyond the Milky Way.
“The experimental techniques developed here provide a new capability to experimentally reproduce pressure-temperature conditions deep in planetary interiors,” lead author and LLNL physicist Ray Smith said in a statement.
While these pressures have been achieved before, those experiments included shock waves that produced temperatures of up to thousands of degrees or more, meaning they are not realistic for planetary interiors. Smith and his colleagues set out to make sure that the temperatures were low enough to be relevant to planets – a feat accomplished by carefully adjusting the rate at which the intensity of the laser changed with time.
The research team used a technique known as ramp compression to avoid the diamond from overheating and melting into liquid carbon, said NewScientist writer Ker Than. Smith’s team fixed a diamond inside a hole that had been cut into a small gold cylinder, and then used precisely-timed laser pulses to strike the interior walls of the cylinder, which caused the gold to emit X-rays that bombarded the diamond itself.
Those X-rays triggered powerful compression waves inside of the stone, and while the experiment only lasted roughly 20 nanoseconds from start to finish, it was slow enough to keep the stone from melting. During the experiment, the scientists were able to compress the diamond to pressures of up to five terapascals and obtain data that can be used to create improved models of gas giants and the diamond believed to be located deep inside of them.
The belief that planets such as Jupiter and Saturn contain diamonds dates back to an October 2013 presentation at the Division for Planetary Sciences of the American Astronomical Society. During that presentation, researchers from the California Specialty Engineering and the University of Wisconsin, Madison explained that these planets could contain solid diamonds at their cores, as well as liquid diamonds deeper within because of higher temperatures.
“Previously, only Uranus and Neptune were thought to have conditions in their interiors that would allow the formation of diamond at their cores,” the researchers explained at the time. “It appears that the interior of Jupiter gets hot enough to reach the liquid diamond region of the carbon phase diagram, whereas the interior of Saturn includes regions of temperature and pressure where carbon could exist as solid diamond.”
While Smith told BBC News that it is unclear whether or not there actually are diamonds in the cores of Jupiter and Saturn, the new research gives scientists the ability to investigate how matter behaves under extreme pressures and temperatures. He added that the experiment gives them a method of “recreating conditions within the cores of giant gas planets – both within our solar system and beyond.”