Meeting report
Huggins, martians and exoplanets
Meeting reports The RAS Ordinary A & G meeting in November included the Gerald Whitrow Lecture
by Prof. Andrew Liddle, while in December Prof. Andrew Collier Cameron gave the George Darwin
Lecture. Both will be reported in future issues. Here Sue Bowler summarizes the other talks.
Unravelling starlight:
William Huggins and
the rise of the new
astronomy
By the light of a watery Moon
Dr Barbara Becker.
The announcement by William
Huggins of his discovery of the
stellar spectrum at the RAS in
1862 was a watershed moment
for astronomy, although it did not
seem so at the time. Spectroscopy
changed astronomy from a focus
on the location of stars to the study
of the chemical properties of stars,
nebulae and novae and, using the
Doppler effect, measurement of the
line-of-sight motion of astronomical objects. Huggins was a pioneer
but also a canny entrepreneur. Our
perception of what he achieved has
been strongly shaped by his own
restrospective account of his career
in The New Astronomy (1897),
which recounts his steady and logical progress, as if in a straight line,
from one goal to the next. Becker’s
examination of his notebooks –
detailed in her book Unravelling
Starlight: William and Margaret
Huggins and the Rise of the New
Astronomy – revealed a different
story, a more complex and gradual
process, more like an irregular path
through a maze, with changes of
direction and dead ends. She sees
The New Astronomy as a carefully constructed account, part of
Huggins’s shrewd – and successful
– career strategy.
Prof. Jay Melosh,
Purdue University, USA.
Could life have
started on Mars
rather than on
Lunar crater seen by NASA’s Moon Mineralogy Mapper on the Chandrayaan-1
Earth? Melosh
spacecraft. (Left): Image shows brightness at shorter infrared wavelengths.
posed the question because there
(Right): Distribution of water-rich minerals (blue) is shown around a small
is good evidence that Mars had a
crater. Both water- and hydroxyl-rich materials were found to be associated
climate early in its history that was
with ejecta from the crater. (ISRO/NASA/JPL-Caltech/USGS/Brown Univ.)
warmer and wetter than it now
is, making it a possible or even
Dr Paul D
probable place for life to evolve. In
of surface minerals, and degassing
Spudis, Lunar
addition, intact rocks from Mars
of the lunar interior. Measurements
and Planetary
have fallen as meteorites on Earth,
from various spacecraft show that
Institute, USA.
so there is a transport mechanism.
the Moon has a hydrosphere, and
Dr Spudis
Melosh pointed out that the notoriit is dynamic, with water moving
described the
ous meteorite ALH84001, in
across the surface, trapped
extensive eviwhich supposed fossils
in craters in permanent
Full
RAS
dence for water on the Moon, long
were described, was
shadow. Radar properties
reports
meetings
assumed to be an essentially dry
also interesting because
of the surface of these
are in The
programme:
body. Lunar topographic mapping,
it had not reached a
craters suggest that the
Observatory
combined with modelling, revealed
temperature over 40 °C
ice layers may be around
http://bit.ly/Vcl5C7
http://bit.ly/
some craters that experience persince it formed, implying
2 m thick, and the number
UMdDy9
manent darkness and some of them,
that the whole transport
of such craters mapped
when measured, proved to be at tem- suggests that there is as much
process – launch, spaceflight
peratures of 25 K, colder than Pluto.
and landing – took place at low temas 600 million tonnes of water ice
Spudis explained that these would
on the Moon. Considering the water peratures where life might survive.
function as cold traps, holding onto
Experiments suggest that dormant
as a source of fuel, life support and
any water that reaches them. Water
spores can survive impacts and in
radiation protection, Spudis argued
sources include meteorite minerals
space, possibly shielded in fractures
that this much quantity of water on
and cometary cores, interplanetary
within rocks. Time is an issue:
the Moon could change the paradust with ice coatings, dust from the digm of spaceflight.
calculations show that martian
Earth’s geotail, solar wind oxidation http://www.lpi.usra.edu/lpi/spudis
meteorites spend tens of millions
of years in space before arriving at
Earth. But microbes can be astona result, anyone hoping to observe
ishingly long-lived; Melosh cited
The planet next door:
a planet needs to understand the
the case of halotolerant organisms
an Earth-mass world
other ways in which a star can prowithin primary salt crystals formed
orbiting Alpha Centauri B duce periodic signals. These include 250 million years ago, that can grow
stellar oscillations, granulation, and now, although normal DNA does
Dr Xavier Dumusque, University
velocity changes associated with
not survive this long. In summary,
of Geneva, Switzerland.
stellar spot cycles. Dumusque then
if viable microbes formed on Mars,
Dr Dumusque described the Earthdescribed how these effects – plus
they could indeed reach Earth.
http://bit.ly/YbBI6Y
mass planet orbiting Alpha Centhose associated with a binary star
tauri B, the second closest star to
system – had to be removed from
Earth, with a period of 3.2, found
their data in order to be sure that
using ESO’s HARPS instrument.
they had found a planet. Alpha
Dumusque described planet-finding Cen Bb gave a radial velocity varitechniques, principally transits and
ation of 0.5 m s –1; at an orbit comparadial velocity, that have been devel- rable to Earth, the signal would be
0.1 m s –1 and currently impossible to
oped since the 1990s to allow the
detect from the surface. However,
tiny signal of a planet to be picked
ESO’s next generation instrument
up. He pointed out that the radial
ESPRESSO, on the VLT from 2016,
velocity signal of an exoplanet is
could detect Earth twins.
so small that it can be confused
http://www.eso.org/public/news/eso1241
The martian meteorite ALH84001.
with changes in its parent star. As
http://bit.ly/ZCWzk5
Becker’s book, published in 2011.
1.12
Are we all martians?:
interplanetary exchange
of living microbes in
meteorites
A&G • February 2013 • Vol. 54