Holes like these on the surface of the moon could be openings to larger caves that might one day contain human bases.
The UW-Madison, with NASA, is looking at how to make us cavemen again.
On the moon. Large, natural, underground shelters may be able to host long-term stays by astronauts, and even anchor permanent bases, if we can find them. Life on the moon is difficult to imagine otherwise — it remains a dark and dangerous place.
“The surface of the moon is very inhospitable,” says Andreas Velten, group leader of the computational optics group at the UW’s laboratory for optical and computational instrumentation.
Much of the lunar surface is made of basalt, rendering it black. Only the thin atmosphere and reflection of the sun’s harsh illumination render it gray. The sun drives one other change, too: temperatures can swing from minus 300 degrees Fahrenheit at night to 240 during the day.
“It would be very hard to have a spacecraft or a space station up there for a very long time,” says Velten. “Humans could not survive on the moon for a significant amount of time without very extensive shielding.”
Caves could shield humans, but finding and exploring them has been out of the question. Until now.
Since 2009 a NASA satellite, the Lunar Reconnaissance Orbiter, has been mapping the surface of the moon, which it circles. Many lava tubes have been discovered. These are long, empty passages through which volcanic lava once flowed. On Earth, lava tubes have been found that are 50 feet wide and 30 miles long.
“These caves are very interesting to NASA for many reasons, including human exploration,” says Velten. Sometimes part of a lava tube’s “ceiling” gives way, opening it to the surface. “The problem right now is… nobody can look in there.”
Velten and his team, with the help of NASA’s Jet Propulsion Laboratory, are developing a way to explore those caves from Earth. The project is called PERISCOPE.
The concept is similar to radar, which sends out radio waves that bounce off things like airplanes and moisture-filled clouds. The time it takes the radio waves to return can be used to calculate distance and basic shapes.
PERISCOPE will do something similar with immensely strong lasers, flashing light into a tube’s opening. The light will reflect off the bottom of the cave, bounce around inside the walls and reflect back to the satellite. “From that...we can reconstruct an image of this tube,” says Velten.
The energy pulse from the satellite will be only a few trillionths of a second long. The satellite itself will have to fly comparatively low — just six miles above the surface — and because of that will require an unstable orbit subject to many course changes. Its life will likely range from a few months to a few years before crashing onto the moon’s surface. Any caves discovered could later be explored by robot.
PERISCOPE is in the design phase, with several students pitching in.
“If we find that this is something that can be done, and done on a reasonable budget, then the next step will be to actually build a system and try it out on Earth,” Velten says. “And eventually design something that will be put on a lunar satellite.”
“It’s a very exciting project,” he adds. “I think there’s a good chance that it might happen.”
Velten is wary of predicting a timeline, pointing to Congress’ changeable support of NASA. “I’d say three to five years may be possible from an engineering standpoint,” he says. After that, there are plenty of other moons and planets.
“There is talk about Mars, for example,” says Velten. “We’re focusing on the moon, we’re designing for the moon. Mars is a little bit of a different challenge.”
Mars has much more reflective surface, but its atmosphere is denser, complicating satellite orbit.
“And the other thing that is actually kind of interesting — on Mars we don’t know whether there’s life in those caves,” says Velten. “There’s the possibility that there’s something alive in there. And then the question is, would you harm them by sending these powerful laser beams in there? So that’s going to be another concern that we have to address.”