U.S. Vice-President Mike Pence stunned the lunar science community last week with the announcement that by 2024, NASA would send astronauts to the Moon’s South Pole. If the Trump Administration and Congress follow through, a crewed mission to this science-rich polar region would offer planetary scientists nothing short of a revolution in solar system science.
A landing precisely at the South Pole is possible, David Kring, a planetary scientist at Houston’s Lunar and Planetary Institute (LPI), told me. It’s on the rim of the 4.2 km-deep Shackleton Crater, some 20 km in diameter and about the size of Houston, he says.
There’s also sunlight there for power and the location has a line of sight to Earth which make for easy communications. However, by 2022, Kring says NASA should have a communications relay satellite in lunar orbit.
The South Pole of the Moon is a highland terrain that is topographically dramatic, says Kring. Qualitatively similar to the sites visited by Apollo 15 and 17, he says the terrain will seem even more dramatic than the U.S. national parks.
As for the first polar landing party?
The Orion crew vehicle can carry four astronauts, but the size of the lunar lander has not been defined, says Kring. But he says the idea is to have at least two astronauts on the surface.
“We have also studied crewed landings at Shackleton and even designed a traverse for astronauts to collect geologic samples,” said Kring. “The principal samples would be regolith samples and perhaps a few boulders, all of which were modified by impact processes.”
The South Pole-Aitken basin, sometimes called the SPA basin, is an enormous 2,500-km-diameter, 13-km-deep impact area. “It is the oldest and largest lunar basin,” said Kring. “Our studies suggest the best place to study the South Pole-Aitken (SPA) basin is the Schrodinger basin, which sits within the SPA basin.”
Out of sight on the far side, Brown University planetary scientist Carle Pieters told me that the SPA is a depression that’s large enough to run from Dallas to San Francisco.
“NASA’s Grail spacecraft has dramatically refined our measure of the moon’s gravity,” said Kring. “So, we will be able to land quite precisely on the lunar surface.”
The highest priority science objective for going to the Aitken basin is to collect a sample of the melt produced by the large impact event that created it, says Kring.
My group’s computer simulations suggest that Aitken Basin was produced by a 170-km diameter asteroid impactor , says Kring. If that occurred on Earth today, he says, it would cause a mass extinction event.
Kring says if new samples determine that the Aitken Basin is relatively close to the age of the Imbrium Basin, that would mean that there was truly a cataclysmic simultaneous bombardment of the Earth and Moon.
“This period in Earth’s history has been geologically erased but it is exquisitely preserved on the Moon,” said Kring.
By determining the cadence of geologic properties that shaped the lunar surface, says Kring, we will be able to determine how dramatically the environment of the Earth and Moon was ravaged. This sequence of events, he says, also ended at the moment that we are first able to detect the origin of life on our planet.
We think that some of those volatiles came from the mantle and were carried upwards in magmas that erupted at the surface, says Kring.
The Moon might have even had a short-lived atmosphere. That’s because so much water, carbon monoxide, carbon dioxide, and sulfur dioxide was potentially released during the Moon’s peak basalt lava production some 3.5 billion years ago. Thus, the Moon might have had an atmosphere for some tens of millions of years, Jeffrey Taylor, a University of Hawaii planetary scientist, told me.
Taylor argues that the best scientific scenario for a 2024 mission is to make it the first mission in a series that establishes a permanent settlement.
The rim of Shackleton Crater is illuminated about 90% of the time; its floor is in permanent shadow, says Taylor. So, he says, from one place you have the energy for long-term exploration and habitation as well as access to permanent shadow and water ice.
And most importantly, Taylor says, this area of the South polar region allows for reasonably rapid economic development of polar ice as a resource. It would first be used for life support and then as propellant for spacecraft.
“I want the mission to lead to a sustainable presence on the Moon with a mix of commercial and governmental projects and money,” said Taylor. “It is the only way we will not just have a one-off mission.”
As for the area’s specific geology?
Terrain around the South Pole is basically a continuation of the bright ‘highlands’ that we know from the near side, says Pieters. One has to head only a few hundred km from the pole toward the equator on the far side before getting into terrain that might represent really interesting deep stuff, she says. That is, potentially lunar mantle material that has been dug up and processed by the SPA basin’s impact history, says Pieters.
“There is no question that the Moon is the best place in the entire solar system to make the greatest advances in our understanding of solar system history,” said Kring. “And the beauty of it is, it’s only three days away.”