8 June 2013 | NewScientist | 17
Radiation too high
for Mars round trip
BAD news for wannabe Mars
explorers. The round trip alone
would blast you with doses of
radiation that come close to the
acceptable limits set by NASA.
Charged, energetic particles like
cosmic rays can wreak havoc on
biological tissue. Earth’s magnetic
field and atmosphere serve to
block or deflect most cosmic rays.
Astronauts on trips to Mars would
be exposed to much higher doses,
but exact figures were unknown.
Now measurements from a
radiation detector on NASA’s
Curiosity rover have been
converted into sieverts, a measure
of how a given dose of radiation
affects the body. A crew on a 180-
day journey to Mars would receive
0.331 sieverts, and the return trip
would bring that up to 0.
(Science, doi.org/mpq). That’s
close to NASA’s lower limit for
risk of exposure-induced death
from cancer over a lifetime – and
doesn’t include any trial runs to
space or time on the Red Planet.
Adding more shielding to the
spacecraft would reduce the dose,
but the best option may be to try
to get there faster, says Curiosity
scientist Cary Zeitlin of the
Southwest Research Institute
in Boulder, Colorado.
Elderly stars like to shred their closest planets
OLD stars make rude hosts. A
survey of ageing stars offers some
of the first direct evidence that
the cantankerous elders often rip
their nearest planets to shreds.
Planet-hunting surveys have
found many sun-like stars with
hot Jupiters, giant worlds in close
orbits. However, hot Jupiters are
rarely found around older stars
called subgiants, which have
burned through their fuel and
puffed up to several times their
original size. This is widely
thought to be because the puffy
stars were up to twice the mass of
the sun when they were younger,
and that might have influenced
where their planets formed.
To help test this notion, Kevin
Schlaufman and Joshua Winn of
the Massachusetts Institute of
Technology tracked the positions
of 142 planet-hosting stars in our
galaxy. Stars are born in clusters
which disperse as they age. More
massive stars burn out faster,
so their elderly populations are
usually found closer together.
But the team found that
subgiants with planets are more
spread out, so are older than
WITH their brutish looks and bulk,
Florida manatees don’t look like
highly sensitive creatures. But in one
way they are: they have a talent for
sensing tiny, nanoscale vibrations.
Sometimes called sea cows, the
manatees live in the shallow waters
of mangroves and seagrass meadows.
Despite their size, they are adept at
navigating muddy waters cluttered
with obstacles like fallen trees. “They
can get up to 30 kilometres an hour
in short bursts, and still navigate
without any trouble,” says Joe Gaspard
of the Mote Marine Laboratory and
Aquarium in Sarasota, Florida.
Their secret is their hair. Gaspard
trained two manatees, Buffett and
Hugh, to approach a vibrating sphere
in the water. If they sensed the
vibration, they nuzzled a paddle and
were rewarded with treats – apples,
carrots, beets and monkey biscuits.
By restricting their hairs with
meshes, Gaspard found that the
hairs on their face and body were
picking up the minuscule vibrations.
Hugh was slightly more sensitive
than Buffett, detecting movements
of just 0.9 nanometres (Journal
of Comparative Physiology A, doi.
I’m picking up good vibrations
expected, meaning that the stars
were probably about the mass
of our sun in their youth. That
means more of them should have
hot Jupiters. So where did they go?
The best conclusion, they say,
is that the stars exerted extreme
gravitational forces as they
swelled up, stretching out their
inner planets until they fell apart.
The finding hints that the same
fate may lie in store for Earth
when the sun puffs up into a
red giant in 6 billion years’ time.
The work has been accepted
by The Astrophysical Journal.
Mon dieu! French
wine is from Italy
FRENCH wine is renowned. But
Parisians would be shocked by the
wine their ancestors started out
making around 500 BC: it was an
Patrick McGovern of the
University of Pennsylvania in
Philadelphia analysed 2500-year-
old amphoras from the south coast
of France at Lattes, formerly Lattara.
This is where Etruscans from what
is now Italy traded with Celtic Gauls.
Amphoras are thought to have
carried wine, but surprisingly, says
McGovern, no one had verified this.
It matters, because Etruscan
amphoras streamed into southern
France from about 600 BC, then a
century later, distinctive local ones
started leaving. If they held wine,
that could reveal a great moment in
European history: the start of French
winemaking, copied from an Italian
model. Archaeologists suspect the
Gauls adopted the Etruscan tipple in
place of their own fermented fruit
and honey drinks, and brought vines
from the eastern Mediterranean so
they could export their own.
Chemicals in the clay show both
Etruscan and local amphoras at
Lattes did hold wine, confirming the
hypothesis for the first time (PNAS,
DOI: 10.1073/pnas.1216126110). It
was no Beaujolais: made of grapes,
yes, but with rosemary and possibly
thyme or basil added, plus pine resin
like modern Greek retsina.
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