Day: January 22, 2018

One of the major issues in sending humans to the Moon – as the United States, China, Russia and Europe want to do (either individually or in some sort of joint venture among some of them) – is where, exactly, to send them. The Moon is an uncompromising place: without any discernible atmosphere or magnetosphere, the lunar surface is open to the full fury of both solar and cosmic radiation. This makes living there without adequate protection somewhat hazardous. Then there is the question of consumables – notably water.

Protection can be found in one of two possible ways: by covering a base under a substantial layer of lunar “soil” – more correctly called regolith – or by placing it underground. While the former is feasible, and could even be achieved via 3D printing, excavating the space needed for a base would be a hefty undertaking, requiring heavy equipment.

However, things could be eased if advantage could be taken of lunar lava tubes. These are natural conduits formed by flowing lava moving beneath the hardened surface of a previous lava flow,  draining lava from a volcano during an eruption. When the lava flow has ceased and the rock has cooled, they can form a long cave, or network of tunnels – some of which can break the lunar surface in what are called “skylights”, resembling  distinctive pits in a landscape. In recent years, over 200 of these pits have been discovered on the Moon’s near side, notably in the great lava plains around the equatorial regions, many of which have been confirmed as entrances to underground lava tubes.

Water is also present on Mars in the form of subsurface ice located around the polar regions – the only parts of the Moon where there is little or no sunlight. If it can be extracted, it could be invaluable to a human presence on the Moon: it could be purified and used for drinking; through electrolysis it could be broken down into its components, hydrogen and oxygen, with the latter used to help maintain the air within a base, the former used alongside carbon dioxide in processes for creating fuel stock space vehicles or surface craft. The difficulty is in accessing the water ice in volume. One way of doing so might be through drilling – although this would again be costly and slow. Another way might be through finding lava tubes which may have become repositories for water ice deposits. The problem is, until now, little evidence for polar region lava tubes has been found.

Pascal Lee, the co-founder and chairman of the Mars Institute, a planetary scientist at the SETI Institute, and the Principal Investigator of the Haughton-Mars Project (HMP) at NASA’s Ames Research Centre – and, totally coincidentally, whom I’ve had the pleasure of meeting a number of times – reports he’s now discovered pits in the north polar region which could be indicative of lava tube skylights.

He found the pits while studying images gathered by NASA’s Lunar Reconnaissance Orbiter of the north-eastern floor of Philolaus Crater, about 550 km (340 mi) from the North Pole, on the lunar near side. They appear as small rimless depressions between 15 to 30 metres (50 to 100 ft) across, with completely shadowed interiors. Most particularly, the pits are located along sections of winding channels criss-crossing the crater floor. Called “sinuous rilles”, these are generally associated with collapsed, or partially collapsed, lava tubes, increasing the possibility they might be skylights leading to intact lava tubes.

“The highest resolution images available for Philolaus Crater do not allow the pits to be identified as lava tube skylights with 100 percent certainty,” Lee states, “but we are looking at good candidates considering simultaneously their size, shape, lighting conditions and geologic setting.”

Should they prove to be entrances to lava tubes, the pits offer an exciting prospect for lunar explorers. They could present a means to access sub-surface water ice – particularly if some of the tubes contain frozen water – which is not yet certain. They might also provide the necessary protection from radiation, making them an ideal location for a subsurface base. If there is water ice in the tunnels, solar collectors ranged on the crater floor could be used to channel heat into the tunnels to melt it, allowing it to be stored and used. A further benefit with Philolaus Crater is that it is one of the Moon’s younger craters, one of the few large craters formed during the Copernican Era formed within the last 1.1 billion years. Scientists located there would be able to study the Moon’s more recent evolution.

In terms of a location for a base, the crater has two additional benefits. The first is that as it is on the lunar near side, it will be in direct line of communication with Earth. The second is more poetic, as Lee himself notes:

We would also have a beautiful view of Earth. The Apollo landing sites were all near the Moon’s equator, such that the Earth was almost directly overhead for the astronauts. But from the Philolaus skylights, Earth would loom just over the crater’s mountainous rim, near the horizon to the south-east.

He continued, “Our next step should be further exploration, to verify whether these pits are truly lava tube skylights, and if they are, whether the lava tubes actually contain ice. This is an exciting possibility that a new generation of caving astronauts or robotic spelunkers could help address” says Lee. “Exploring lava tubes on the Moon will also prepare us for the exploration of lava tubes on Mars. There, we will face the prospect of expanding our search for life into the deeper underground of Mars where we might find environments that are warmer, wetter, and more sheltered than at the surface.”

Continue reading “Space Sunday: lava tubes and politics” →