SPACE
& SCIENCE NEWS: May 2003
Home > Space
& Science News > Space & Science News: May 2003
SARS from the stars?
(May 24, 2003)
In a letter to the British medical journal The Lancet, Chandra
Wickramasinghe
of the Cardiff Centre for Astrobiology, and his colleagues, argue
that the SARS virus is extraterrestrial in origin. Wickramasinghe
is a leading advocate of the panspermia
hypothesis and, in particular, that many global outbreaks of disease,
including 'flu epidemics, are caused by organisms arriving from space,
building up in the stratosphere, and then raining down on the Earth's
surface. In their recent communication to The Lancet, Wickramasinghe
et al. write: "With respect to the SARS outbreak, a prima facie case
for a possible space incidence can already be made. First, the virus
is unexpectedly novel, and appeared without warning in mainland China.
A small amount of the culprit virus introduced into the stratosphere
could make a first tentative fall out East of the great mountain range
of the Himalayas, where the stratosphere is thinnest, followed by
sporadic deposits in neighbouring areas. If the virus is only minimally
infective, as it seems to be, the subsequent course of its global
progress will depend on stratospheric transport and mixing, leading
to a fall out continuing seasonally over a few years. Although all
reasonable attempts to contain the infective spread of SARS should
be continued, we should remain vigilant for the appearance of new
foci (unconnected with infective contacts or with China) almost anywhere
on the planet. New cases might continue to appear until the stratospheric
supply of the causative agent becomes exhausted." Wickramasinghe's
views remain highly controversial and his recent comments about the
SARS virus have received short shrift from the medical research community.
Visit the Cardiff Centre for Astrobiology's website here
and The Lancet here. |
Where Mars life might be
(May 24, 2003)
The best place to look for life near the surface of Mars today may
be the mysterious Russell Crater in the Martian southern hemisphere
at 54.5°S, 347.3°W. Two German researchers, Dennis Reiss and
Ralf Jaumann, conclude (see reference below) that remarkable features
in Russell Crater, shown in the photo here by Mars Global Surveyor,
resemble terrestrial mudflows. (The image covers an area about 3 km
across and shows one very large sand dune; the surface slopes from
upper right toward lower left.) Observations of the region made during
the local autumn and spring, when frost covers the dunes and then
recedes, indicate liquid water may be present on the surface at certain
times of the year. This water may be mixing with soil to create frequent
mudflows which are possibly the youngest features on Mars, perhaps
even forming from time to time during the present day. When winter
arrives at Russell Crater, water vapour and carbon dioxide condense
out of Mars' thin atmosphere and frost the dunes. Temperature and
albedo (reflectivity) readings indicate that during the spring thaw,
the frozen carbon dioxide sublimates – turns directly into a
gas – leaving a thawed surface containing liquid water. In this
place, for a few hours each day, just after noon in the summer, there
could be liquid water on, or just below, the surface of Mars –
an intriguing possibility for those in search of Martian life. Unfortunately,
none of the spacecraft due to land on Mars in 2003-4 will go anywhere
near Russell Crater: Beagle
2 will land on Issidis Planitia, about 10 degrees north of the
equator, while the two Mars
Exploration Rovers will touch down near the equator, halfway around
the planet from each other.
Read the abstract of Reiss and Ralf's work, published in Geophysical
Research Letters, here. |
How alien can alien life be?
(May 2, 2003)
The alien from the "Alien"
movies looks fantastically unfriendly and xenomorphic. But, in fact,
it's probably hopelessly anthropomorphic
in design: bipedal, hominoid torso, head with mouth and teeth, etc.
Life "out there" might be more alien that we can possibly imagine.
It could be wildly unfamiliar at the most basic level (Silicon
instead of carbon?
Ammonia instead
of water? Energy instead
of matter?) and/or remarkably unlike us at the gross level of appendages,
sensory organs, brain structure, and so on. However, if we find extraterrestrial
life that, like all Earth life, uses DNA
for carrying its genetic code, then it may not have much leeway in
deciding how that DNA is structured. Terrestrial life uses DNA with
four bases – guanine,
adenine, thymine,
and cytosine. Scientists
from New Zealand and Sweden have built a computer model to show that
either 4 or 6 is the likeliest number of bases for life that uses
DNA anywhere in the Universe. Paul Gardner and colleagues at Massey
University, New Zealand, and Uppsala University, Sweden, simulated
the progression from the hypothetical, primordial RNA
World to the current DNA-dominated world. RNA is chemically similar
to DNA but is much less stable and so less suitable for holding the
blueprint information for building complex organisms. RNA World theorists
think that RNA developed from simpler chemicals and only later evolved
into DNA. Gardner and his colleagues programed a supercomputer to
look at how RNA might have developed had it had 2, 6 or 8 bases, as
well as the familiar 4. They found that 4- and 6-base RNA molecules
were the most efficient at evolving into DNA. The 2- and 8-base RNAs
got stuck somewhere along the evolution process. Four-base RNAs seemed
best suited to overcoming RNA's greatest weakness: its susceptibility
to making errors as it copies itself. However, if RNA-based lifeforms
had developed the error-correcting techniques needed to repair the
damage to their genetic code caused by mutation and degeneration,
it's possible they might have developed into something with six-base
DNA. |
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