Pressure at the centre of Saturn created on Earth

This Oct. 6, 2004 photo provided by NASA, taken by the Cassini Saturn Probe, shows the planet Saturn and its rings. One of the most evocative mysteries of the solar system, where Saturn got its stunning rings, may actually be a case of cosmic murder with an unnamed moon of Saturn, that disappeared about 4.5 billion years ago, as the potential victim. Suspicion has fallen on a disk of hydrogen gas, that surrounded Saturn when its dozens of moons were forming, but has now fled the scene. And the cause of death? A possible forced plunge into Saturn. (AP Photo/NASA)

What do you think is the highest pressure that can be produced and studied in the lab?

A recent experiment just hit the answer with a mind-boggling number of five terapascals, which amounts to 50 million atmospheres — “a pressure similar to that at the centre of Saturn.”

Not just this, it has mimicked on earth what can happen to matter at the centres of distant, massive exoplanets. The paper by R.F. Smith et al , is published today (July 17) in Nature .

Dr. Smith is from Lawrence Livermore National Laboratory, Livermore, California.

One of the questions that has been of interest to scientists in recent times is how matter behaves under pressures that are a million or billion times more than what we experience on earth.

This question gains importance with the discovery of huge numbers of massive planets outside our solar system, where matter may exist under such high pressure conditions.

Now, experiments have made it possible to study such high pressures in the lab. Pressures up to 5 terapascals have been realised at the U.S. National Ignition Facility using the world’s largest laser to generate this pressure by increasing the pressure in steps (ramp-loading). Using 176 laser beams, the pressure was applied on nanocrystalline diamond samples and the changes were observed.

Theories of how matter behaves under pressure may break down under such large pressures, so it is necessary to have experiments that can mimic these high pressures and observe how materials transform under these pressures.

Then comparing the predictions of a theory to the observed patterns can help confirm whether the theory holds good — very different from extrapolating based on what we know of matter under earth conditions.

In this case, the density functional theory (DFT), which is a quantum mechanical theory of condensed phases of matter, appears to make predictions that are in agreement with the results of the experiment.

The experimental techniques developed at the Facility can create the pressure-temperature conditions that prevail deep inside these massive “super earth” exoplanets which are rich in carbon.

This augurs well for future studies of these planets in earth-based laboratories.