The far side South Pole-Aitken (SPA) basin, the largest impact basin on the Moon (diameter = 2500... [+]
Despite depleted budgets, NASA and the broader lunar science community are both still talking manned lunar missions --- potentially, in 2021 to the earth-moon L2 Lagrange point (60,000 kms above the far side surface) and a manned far side surface mission by 2028.
“The first flight test of the [new] Orion spacecraft is scheduled for September 2014,” said David Kring, planetary scientist at the NASA-funded Lunar and Planetary Institute (LPI) in Houston. “Orion is then scheduled to fly around the moon without crew in 2017 and then a crewed orbital lunar mission in 2021.”
Although currently, there’s no formal NASA funding for a specific crewed lunar mission, Kring says the U.S. agency has already planned space-based tests for the Orion spacecraft.
Kring says Orion spacecraft “parked” at the L2 position could simultaneously maintain communications with both the earth and lunar far side.
But Kring says ultimately we would need rovers and astronauts on the far side.
“You can’t truly understand a place thoroughly without humans actually being there,” said Kring. “It’s as if we were trying to decipher earth from a weather satellite.”
Kring says such long manned absences from the lunar surface have been a hindrance to all of planetary science. It’s been more than 40 years since Apollo 17 departed the lunar near side’s Taurus-Littrow valley.
“This absence from the lunar surface has undermined progress in lunar geology and in all of planetary science,” said Kring.
NASA’s heavy-lifting Space Launch System (SLS) and a Lockheed Martin-built Orion Multi-purpose Crew Vehicle spacecraft could change all that by using the moon’s gravity to slingshot into an L2 parking orbit. Traveling some 15 percent farther than Apollo did from earth, such a crewed mission could spend at least two weeks in deep space.
“All four of Orion’s crew could go to the lunar surface,” said Kring, using newly-tested manned lunar rovers, each designed for a crew of two. The idea would be to either use two such rovers during the same mission, or alternate crew between one rover and the “parked” Orion spacecraft.
The number one science priority, says Kring, is to test the Lunar Cataclysm hypothesis --- the idea that during a period of Late Heavy Bombardment in our young inner solar system, the earth and moon were severely bombarded by large impactors some 4 billion years ago. The next priority, he says, is to figure out just how old the 2500 km-diameter South Pole Aitken Basin truly is.
On the Western rim of the Aitken Basin, there’s a potentially science-rich basin within a basin. The 3.8 billion year old 320-km diameter Schrodinger Basin centered at 75 degrees south lunar latitude, lies within the much larger South Pole Aitken Basin.
Within Schrodinger’s 150 km-diameter inner ring, Kring says exposed large boulders, some 25 to 30 meters in size would make “wonderful targets” for sample return.
A lunar return mission would also test the Giant Impact lunar-formation hypothesis in which within 30 million years of earth’s formation, a Mars-sized planetary embryo slammed into nascent earth, sending molten debris into earth orbit; creating the moon in the process.
Theorists think that very soon after the moon’s tumultuous formation, it would have become orbitally-locked with earth, causing its far side to always be hidden from earth.
“We don’t have a large number of rock samples against which to test the [moon-forming] hypothesis,” said Kring. But he says rocks in the peak ring of Schrodinger would have isotopic compositions indicative of the material from which the moon accreted.
Kring says rocks from the Apollo missions are too young to carry the signatures of these early lunar events.
However, the South Pole lunar Aitken Basin is thought have been hit by an estimated civilization-ending, 170 km-sized impactor as early as 4.35 billion years ago. Schrodinger basin is thought to have been created by a 10 to 20 km-sized impactor some half a billion years later.
Kring says the same processes that were reshaping the moon some 4 billion years ago likely affected the origin and early evolution of life on earth.
At the time, our own planet would have been bombarded with impactors that may have created at least 20,000 craters each more than 20 kms in diameter. During the same period of Late Heavy Bombardment, earth may have seen some 40 impact basins, each of a 1000 kms or more, with some as large as 5000 kms in diameter.
“Every time we go to the moon,” said Kring, “we get a better understanding of our own earth.”
In addition to lunar science, exploration of Schrodinger crater --- which has one of the biggest far side pyroclastic deposits --- could determine whether the moon has recoverable volatile elements --- everything from oxygen to hydrogen to zinc, that could be used in situ to make building materials, fuel, even water.
Although a crewed mission lunar lander still needs to be developed, as Kring notes: “We are ready to land on the moon with crew or robotic assets as soon as given an opportunity.”
