Pigment found in ancient cave paintings headed for outer space

PARIS, Feb. 12 (UPI) -- A pigment once used in prehistoric cave paintings -- burnt bone charcoal -- will protect a European space mission from the Sun's close-up glare, scientists say.

The European Space Agency's Solar Orbiter, due for launch in 2017, will perform high-resolution imaging of our parent star from as close as 26 million miles, a little more than a quarter of the distance to Earth.

The spacecraft must endure 13 times the intensity of terrestrial sunlight and temperatures as high as 960 degrees Fahrenheit, mandating a search for a material that could endure such punishment, ESA said in a release Wednesday.

"We soon identified a problem with the heatshield requirements," ESA materials technology specialist Andrew Norman said.

"To go on absorbing sunlight, then convert it into infrared to radiate back out to space, its surface material needs to maintain constant 'thermo-optical properties' -- keep the same color despite years of exposure to extreme ultraviolet radiation.

"At the same time, the shield cannot shed material or outgas vapor, because of the risk of contaminating Solar Orbiter's highly sensitive instruments," he said.

The answer was found outside the space business, he said, with Irish company Enbio and its CoBlast technique, originally developed to coat titanium medical implants.

The process removes the surface oxide layer found on reactive metals like titanium, aluminium and stainless steel while simultaneously replacing it with a material dubbed "Solar Black" -- processed from burnt bone charcoal like that found in cave paintings.

"The big advantage is that the new layer ends up bonded, rather than only painted or stuck on," Enbio Managing Director John O'Donoghue said. "It effectively becomes part of the metal -- when you handle metal you never worry about its surface coming off in your hands."