NASA is set to send a $280 million (£180m) probe to the Moon to solve a celestial mystery first raised by its Apollo-era pioneers.
More than four decades after astronauts witnessed a cryptic glow on the lunar horizon, the US space agency aims to gather data that is likely to explain the phenomenon and shake up theories about the Moon’s barely-there atmosphere.
The Lunar Atmosphere and Dust Environment Explorer (LADEE), a 7.7-foot (2.37 metre) robotic spacecraft due for launch from Virginia tonight on a rocket built from decommissioned Cold War intercontinental ballistic missiles, will conduct a 100-day study of the gaseous envelope surrounding the Moon.
“Other spacecraft and instruments have been launched to the Moon before, but nothing like this robotic mission with its purpose and ability to precisely measure the environment above the lunar surface,” said Brian Day, director of education and public outreach at Nasa’s lunar science institute in California.
By conducting a detailed examination of the Moon’s exosphere, Nasa hopes to also gain new insight into Earth’s own atmosphere and the development of other worlds that lie beyond, such as Venus and Mars.
“As the most accessible planetary body besides Earth, and as one that is thought to have changed little since its initial development – unlike Earth, Mars and Venus – the Moon offers a unique look into the distant past of planetary evolution,” states Nasa’s mission overview.
Questions about the composition of the Moon’s atmosphere arose during robotic and human explorations of the Moon in the 1960s and 1970s.
In 1972, the last man to walk on the Moon – Eugene Cernan, commander of the Apollo 17 mission – sketched the sun rising over the lunar surface and shared it with scientists upon his return. He had expected to see just a dim glow that would grow in size and brilliance as the light spilled over the horizon, but what he witnessed instead was a phenomenon that made little scientific sense, as the sun’s rays crept across the Moon in a strange pattern. The light show was also witnessed by astronauts on three preceding Apollo
On Earth, the same pattern of glowing “streamers” they saw is created at sunrise and sunset by light bouncing off dust and moisture in the atmosphere. But on the Moon there is next to no atmosphere, and no wind to whip up the dust – thus creating a mystery as to how the sunlight was being reflected in such a way.
LADEE will investigate and seek to explain the phenomenon, which scientists now believe could be to do with lunar dust undergoing a process of becoming electrically charged and then propelled to high altitudes by electrostatic forces.
“What we hope to learn from LADEE is a means to gain a better understanding of the structure and composition of the very thin atmosphere of the Moon... and also how much dust may be in the lunar atmosphere,” said Mr Day.
LADEE is due to lift off at 11:27pm local time tonight (4:27am BST Saturday) from Nasa’s Wallops Island launch facility in Virginia.