Underground lava tubes can house humans on the moon and earth

[hab...@anony.net]

http://www.bbc.co.uk/news/science-environment-31953052

Lava tubes safe enough for Moon base
19 March 2015 Last updated at 14:10 By Paul Rincon Science editor,
BBC News website, The Woodlands, Texas This lava tube is in Hawaii,
but the features could be even bigger on the Moon
Natural tunnels known as lava tubes could safely house permanent bases
on the Moon, scientists have said.

The underground volcanic structures have previously been proposed as
ideal sites for human settlements.

Scientists have now assessed how stable these features might be, and
found that tubes of 1km in size and bigger would be structurally
sound.

They could protect against the challenges posed by the lunar
environment.

Details of the work were presented at the 46th Lunar and Planetary
Science Conference (LPSC) in Texas.

Unlike Earth, the Moon lacks a thick atmosphere and magnetic field to
protect it against cosmic radiation. The absence of an atmospheric
buffer also means that the Moon's surface receives more frequent
meteorite impacts and more extremes of temperature.

For example, the Moon's surface temperature can vary by several
hundred degrees C during the course of a lunar day.

Cave entrances like this one in Mare Tranquilitatis may open into
lava tubes
But housing bases underground, inside lava tubes, could offer
shielding against these risks.

The lunar tunnels are expected to be larger than those already
discovered on our planet, because of the Moon's lower gravity. No-one
has yet definitively discovered an example on the Moon, but spacecraft
have revealed cave entrances called skylights that may open into lava
tubes.

Using existing data, David Blair and colleagues from Purdue University
in West Lafayette used computer modelling to determine the stability
of lunar lava tubes with different widths, roof shapes and roof
thicknesses.

"It's the first modern re-assessment of how stable these can be," he
told BBC News.

He found that tunnels with widths of 1km and greater could remain
standing beneath the lunar surface.

Lunar lava tubes should be stable up to about 5km wide
In his poster at the meeting, he displayed a diagram showing his home
town of Philadelphia sitting neatly within a lava tube with a width of
5km - which was found to be the rough theoretical maximum for
stability.

The underground structures are thought to have been formed during
basaltic lava flows during the Moon's history. When the upper layer of
a lava flow cools and hardens, molten rock may continue to flow
beneath it. Once this drains, it can leave behind a hollow space.

Long, snaking features on the Moon called sinuous rilles are thought
by some to be lava tubes that have collapsed in on themselves.
However, this interpretation is controversial among scientists.

Nonetheless, researchers are continuing to look for clear evidence of
their existence in spacecraft data.

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