Earth's magnetic field -- A hazard for lunar astronauts? (Forwarded)

Royal Astronomical Society
London, U.K.

Issued by RAS Press Officers:

Robert Massey
Tel: +44 (0)20 7734 4582
AND
Anita Heward
Tel: +44 (0)1483 420 904

NATIONAL ASTRONOMY MEETING PRESS ROOM (16 - 20 APRIL ONLY):
Tel: +44 (0)1772 892 613
+44 (0)1772 892 475
+44 (0)1772 892 477

RAS Web site:
http://www.ras.org.uk/

RAS National Astronomy Meeting web site:
http://nam2007.uclan.ac.uk

CONTACT:

Dr Mike Hapgood
Space Science and Technology Department
Rutherford Appleton Laboratory
Tel: +44 (0) 1235 44 6520

From 16 to 20 April, Dr Hapgood can be contacted via the NAM press office
(see above).

PRESS INFORMATION NOTE: RAS PN 07/07 (NAM 03)

EMBARGOED FOR 00:01 BST, 16 APRIL 2007

EARTH'S MAGNETIC FIELD -- A HAZARD FOR LUNAR ASTRONAUTS?

For four days every month the Moon passes through the magnetic field of
the Earth and parts of the lunar surface are charged with static
electricity. Next week Dr Mike Hapgood of the Rutherford Appleton
Laboratory will present a model at the Royal Astronomical Society National
Astronomy Meeting in Preston, which suggests that this charging may
increase after the year 2012 and become an important issue for future
lunar explorers.

Once in every orbit around the Earth the Moon moves through the magnetic
tail -- the region on the nightside of the Earth where the magnetic field
is drawn out into a million or more kilometre long tail pointing away from
the Sun. In the middle of the tail there is a region full of energetic
electrons and other charged particles (the plasmasheet). When the Moon
passes through the plasmasheet these electrons can collect on parts of the
lunar surface and charge them with static electricity. Observations from
NASA's Lunar Prospector spacecraft during 1998 confirm the existence of
this charging.

Dr Hapgood's model suggests that the exposure of the Moon to plasmasheet
charging varies markedly over an 18-year cycle linked to changes in the
Moon's orbit. This exposure was low at the time of the Apollo landings in
the early 1970s and is low again today -- but it was high in the 1990s and
will rise again after 2012. The United States, Russia, India, Japan and
China have all announced plans to send astronauts back to the Moon around
the year 2020 -- at the time when lunar surface charging is predicted to
be high.

Lunar surface charging may be an important issue for future lunar
exploration because it increases the risk of electric discharges, which
can interfere with and damage sensitive electronics. It may also affect
the behaviour of lunar dust, which is a recognised hazard for lunar
astronauts as it can easily enter spacesuits, living quarters and
equipment.

Dr Hapgood comments, "Electrical charging is one of the less well-known
natural hazards of spaceflight. It's important to understand it how this
affects the Moon so spacecraft designers can use scientific knowledge to
protect future explorers."

NOTES FOR EDITORS

The 2007 RAS National Astronomy Meeting is hosted by the University of
Central Lancashire. It is sponsored by the Royal Astronomical Society and
the UK Science and Technology Facilities Council.

This year the NAM is being held together with the UK Solar Physics (UKSP)
and Magnetosphere, Ionosphere and Solar-Terrestrial (MIST) spring
meetings. 2007 is International Heliophysical Year.

IMAGE CAPTIONS:

[Image 1:
http://www.nam2007.uclan.ac.uk/press...20070416a1.gif (1.1MB)]
An animation of the Moon (the small white circle) crossing the
magnetospheric tail (the blue circle) around Christmas 2007 (the time is
shown at the upper left). The view is from the Earth looking away from the
Sun. The Moon crosses from right to left and occasionally encounters the
plasmasheet (red). The two distance scales are in units of multiples of
the radius of the Earth (Re).

[Image 2:
http://www.nam2007.uclan.ac.uk/press...20070416a2.png (21KB)]
A graph of the predicted lunar exposure to charging by the plasmasheet
over the years 1960 to 2030. The red trace shows the monthly exposure,
which also varies with the seasons (peaking in June and December). The
blue line is a smoothed curve that highlights the 18 year cycle.