Download Global Surveyor finds stripes on Mars

NEWS
Global Surveyor finds stripes on Mars
NEWS IN BRIEF
RAS Reception at AAS
RAS members are invited to a
reception at the 207th Meeting
of the American Astronomical
Society, Washington DC, (8–12
January 2006), on Tuesday 10
January 2006, 6.30–7.30pm at
the meeting venue, the Marriott
Wardman Park Hotel. Members
are welcome to bring a guest,
especially anyone interested in
becoming a Fellow of the RAS.
Simon Mitton will say a few
words about Sir Fred Hoyle
(President of the RAS 1971–73)
and there will be a free draw
for copies of his recent
biography of Sir Fred.
Contact Jacqueline Mitton:
[email protected]
NAM 2006
A high-resolution map of remanent magnetism in the rocks of
Mars, made by NASA’s Mars
Global Surveyor, has found
stripes of alternating magnetic
polarity comparable to those
found in the Earth’s ocean floors.
The magnetic stripes on Earth
formed when the ocean crust was
formed, rolling out like a conveyor
belt from the mid-ocean ridges, as a
consequence of plate tectonics. The
similar pattern in ancient rocks on
Mars suggests that plate tectonics
once operated there, very early in
the planet’s history. There are also
discontinuities in the pattern of the
stripes, which look like another
plate tectonic feature on Earth,
transform faults, which reinforces
the suggestion. Lines of volcanoes in
Tharsis and major faults within Cerberus Fossae also align in the directions expected if they had a similar
plate tectonic origin.
Although the stripes are much
broader than those on the Earth’s
ocean floor, they correspond to the
size expected for Earth’s striping if
measured in the same way as Mars
Global Surveyor. The map is
described by Connery et al. in the
Proceedings of the National Academy of Science vol. 42, no. 42, and
available at
http://www.pnas.org
Cluster and Double Star see massive ‘starquake’
Unique data obtained by ESA’s
Cluster and joint Chinese/ESA
Double Star missions have provided the first evidence of cracks
on the crust of a neutron star. The
cracks originated at the start of
the biggest “starquake” ever
recorded on a neutron star. This
flotilla of satellites were able to
pin down events in the first 100
milliseconds of radiation received,
establishing, among other things
that a crack around 5 kilometres
across formed on the neutron
star, writes Peter Bond.
On 27 December 2004 the radiation from an extremely powerful
explosion on the surface of neutron
star SGR 1806-20 reached Earth and
continued for more than six minutes.
In the first 200 milliseconds the
amount of energy released was equivalent to what our Sun radiates in
250 000 years, making this the
brightest event originating outside
our solar system to be recorded on
Earth.
Several scientific satellites observed
the giant flare, including ESA’s
A&G • December 2005 • Vol. 46
gamma-ray observatory Integral. For
those first bright milliseconds, the
blast blinded almost all instruments
on γ-ray satellites observing that
region of the sky. But the particle
detectors onboard the flotilla of Cluster and Double Star satellites,
designed to study Earth’s magnetosphere, could observe the blast for its
whole duration without being
blinded.
“The unique Cluster and Double
Star data provide the first evidence of
three separate timescales within the
first 100 milliseconds of this event,”
said Steve J Schwartz, lead author of
the article in the Astrophysical Journal, from Imperial College London.
“It is based on the characteristics of
these timescales, combined with theoretical models, that we could draw a
scenario on what happened in
SGR 1806-20.”
Schwartz and colleagues provide
the first observational evidence that
the giant flare was produced when
the crust of the magnetar could no
longer plastically compensate the
internal magnetic stress and finally
cracked. One of the three timescales
even allowed the estimation of the
fracture size: about 5 kilometres
across. This is a significant size considering that SGR 1806-20 has been
estimated to be a sphere of only a few
tens of kilometres in diameter.
Schwartz combined these findings
with other results on the SGR 180620 starquake obtained by Italian
astronomer Gianluca Israel, from
INAF-Osservatorio Astronomico di
Roma, and colleagues. These results,
based on NASA’s Rossi X-ray Timing
Explorer data, revealed the presence
of quasi-periodic oscillations in the
energy emitted by the neutron star
towards the end of its super-blast.
“These oscillatory modes are likely
to be associated with global seismic
oscillations. In particular, the large
crustal fracturing inferred by us can
easily excite oscillation modes with
characteristic frequencies in the range
we observed,” said Prof. Schwartz.
These findings appear in the Astrophysical Journal (ApJ 627: L129–
L132, 2005 and ApJ 628: L53–L56,
2005).
The RAS National Astronomy
Meeting 2006 will be held at the
University of Leicester, from 3–7
April next year. As well as 16
plenary sessions and 18
sessions of submitted talks,
there will be an extensive poster
session, in which posters will be
judged for prizes. Participants
will also be able to attend an
event at the National Space
Centre, and a public lecture on
solar system science. NAM
2006 will also include the RAS
George Darwin Lecture.
You can find out more about
registration at the dedicated
website, or from organizer
Prof. Bob Warwick in the
Department of Physics and
Astronomy at Leicester.
http://www.nam2006.le.ac.uk
EAAE summer school
The European Association for
Astronomy Education is holding
its 10th Summer School for
primary and secondary
teachers from 3 to 9 July 2006
in Santa Cruz de La Palma.
Around 60 European teachers
will attend general lectures,
working groups, workshops and
observational sessions. It is not
aimed at experts and the
presentations will be in English.
The closing date for registration
is 30 April and the approximate
cost of registration and
accommodation is €750. British
Council support may be
available. Anyone interested
should contact:
Alan_C_Pickwick@btinternet
.com or telephone 0161 973
6796.
http://www.algonet.se/~sirius/
eaae.htm
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