LONELY PLANET: OUR PLACE IN SPACE MAY BE UNIQUELY ADVANTAGEOUS TO
INTELLIGENT LIFE
From Boston Globe, 3 November 2002
INTELLIGENT LIFE
From Boston Globe, 3 November 2002
http://www.boston.com/dailyglobe2/307/focus/Lonely_planet+.shtml
Scientists debate the existence of intelligent life beyond Cambridge
By Jascha Hoffman, 11/3/2002
HERE ARE ABOUT 100 billion galaxies in the observable universe, each with
hundreds of billions of stars. What are the chances that there's any
interesting life out there?
In 1961, astronomer Frank Drake proposed a simple answer: We can assume that
some stars have planets, some planets host single-celled life forms, some of
those life forms survive to develop intelligence, and some intelligent
beings leave an electromagnetic trace before they expire.
Carl Sagan once estimated that in the Milky Way alone there must be over a
million detectable civilizations. Today, Drake sticks to his original
estimate of 10,000.
Peter Ward is sick of these loose overestimates. ''You can't turn on the TV
without seeing aliens,'' the co-author of ''Rare Earth: Why Complex Life is
Uncommon in the Universe'' (Copernicus Books, 2000) complained to a
Cambridge auditorium packed with astronomers, UFO enthusiasts, and other
onlookers last week. Ward was facing off against Harvard paleontologist
Charles Marshall at a debate hosted by the Harvard-Smithsonian Center for
Astrophysics. In 1996, Ward and Marshall worked together on a paper arguing
that a major drop in sea level, in addition to the infamous asteroid, had
wiped out the dinosaurs. But when it comes to the distribution of
intelligent life in the universe, they couldn't agree less.
"Maybe I shouldn't count myself as intelligent life," quipped Ward, a
professor of geology at the University of Washington. ''The first stop on my
book tour was a science fiction convention. A little girl told me I was the
devil for taking the aliens away.'' The Australia-born Marshall, for his
part, retains the taste for discovery that propelled him from childhood
dino-mania to a career in evolutionary biology. ''Life is capable of more
trajectories than physics or astronomy might predict,'' he said. ''I don't
know if life is teeming out there. But it could be.''
Ward and Marshall agree that the universe is full of microbes. Recent
studies have shown that interstellar clouds can generate amino acids, the
building blocks of proteins. Meteors falling to earth usually contain a
variety of organic compounds. And cells can survive under extremes of
temperature, pressure, and pH, and may be able to travel from planet to
planet on comets.
But to flourish, even simple life needs liquid water, and this limits it to
planets in the habitable zone: far enough from a star not to be boiling, but
close enough not to be freezing. And to get complex life - anything more
intricate than a flatworm - it seems that you need, first of all, a decent
atmosphere.
Here on Earth, it took 3 billion years of steady temperatures to build up
enough oxygen to support animals. The fact that our planet lies in a
habitable zone does not itself guarantee such steadiness. Ward thinks that
plate tectonics also do us a great service: When one plate slides under
another, an updraft of magma brings carbon dioxide to the surface,
eventually warming up the atmosphere through the greenhouse effect. But once
the atmosphere gets warmer, excess carbon dioxide is removed by the calcium
in the magma, and it gets cooler again. ''For billions of years, we've been
bouncing around in a very fine temperature range because of the thermostat
of plate tectonics,'' he said. ''How common is that in the universe? We
don't know.''
To survive long enough to evolve any complexity, Ward went on, life must
also avoid being destroyed by space debris. Earth is shielded by Jupiter's
gravitational field, which slows down incoming comets. But in most solar
systems, a Jupiter-sized planet has such an erratic orbit that it will
eventually fling any nearby planet away from the star. We may be uniquely
lucky to live in such a safe neighborhood.
Marshall is unimpressed by scenarios that emphasize life's fragility. "The
question is, how hard is it to sterilize a planet?" he asked. In the total
devastation following the Mount Saint Helens eruption, biologists were
staggered to find plants protected by animals that fell on them. Even at
Hiroshima, a few people survived at close range to the explosion. ''We
should expect such surprises,'' said Marshall. ''Life will find a way.''
Life also makes its own way. Take the Cambrian explosion of 445 million
years ago, when a host of scuttling sea creatures burst into a world that
hadn't seen much more than worms. What accounts for such rapid evolutionary
change? ''If you have a bunch of plant life, and someone is able to develop
a few genes for jaws, then everyone had better watch out,'' said Marshall.
It's no surprise that eyes and legs, crucial for hiding from predators,
appeared at the same time. ''With an increase in selective pressures,
complexity is bound to arise. You don't need special conditions.''
But Peter Ward was not convinced. ''If complexity is inevitable, then what
was going on for the three billion years between the first cell and the
Cambrian explosion?'' Just a slow and steady buildup of oxygen due to the
presence of simple life-forms and liquid water. ''Without the thermostat of
plate tectonics, the right conditions just don't last very long,'' he said.
Of course, there may be more to life than what we can guess now. ''We have
some idea of what conditions were necessary for us to evolve,'' Marshall
said, ''but we don't know if they're the only possible ones.'' While Ward
prefers to limit the discussion to life as we know it - carbon-based
organisms with DNA - Marshall thinks we should expect the unexpected.
Some audience members found this approach a bit too vague. ''One data point
is better than none,'' one said. ''Can you quantify the problem?''
Many scientists are working on it. Astrobiology, defined broadly as the
study of life in the universe, is now serious science. NASA and the National
Science Foundation invest tens of millions of dollars every year in it.
Astronomers search for new planets, geologists prospect for evidence of
water on already known planets, and biochemists piece together the origins
of life on earth. Still, it's mostly theory for now. And hitchhiking to the
nearest star still takes 300,000 years.
''The fact that neither of us has any numbers, shows that we're going on
next to nothing,'' said Marshall. ''But my sense of faith is that the
universe is so unimaginably rich that it will turn out that life is common,
and that scientific reasoning, while powerful, can lock us into a narrow
view of what is possible.''
Jascha Hoffman is a writer based in Boston
This story ran on page D1 of the Boston Globe on 11/3/2002.
Copyright 2002, The Boston Globe
=============
(8) MOON MIGHT REVEAL FIRST LIFE ON EARTH
From Nature Science Update, 2 November 2002
http://www.nature.com/nsu/021028/021028-13.html
Lunar rocks retain memories long since lost down here.
TOM CLARKE
The surface of the moon is spattered with over 8 million tonnes of the
Earth, astronomers have estimated. A mission to collect and study this
planetary shrapnel could provide unique insights into the origins of life
and the planets, they say1.
Asteroids and comets have pelted the Earth, Mars and Venus since the Solar
System formed. The barrage peaked during a period known as the Late Heavy
Bombardment, around 3.9 billion years ago.
The moon "witnessed and recorded all this", says John Armstrong of the
University of Washington, Seattle. Our companion formed in a massive
collision between the Earth and a Mars-sized object around 4.5 billion years
ago.
Armstrong and his colleagues estimated the impacts on the Earth by measuring
the number and size of craters on the Moon. They then calculated how much of
the Earth these collisions would have hurled into space, and the probability
that this rubble hit the Moon.
A 100-square-kilometre patch of the Moon contains about 20 tonnes of Earth
fragments, the team reckons. The same area contains around 180 kilograms of
Mars and 80 of Venus.
Collecting pieces of the three planets would let us compare their origins.
"It could end all the speculation about what the early planets were like,"
says Armstrong.
Reach for the Moon
The origins of life on Earth are hotly debated, partly because there are no
rocks older than about 3.8 billion years. Erosion and continental drift have
wiped the slate clean over and over.
But the Moon has remained largely untouched - except by asteroids - since it
formed. Pieces of the Earth littering its surface would be of all ages,
although most would date from the Late Heavy Bombardment, says Armstrong.
They could reveal the chemical signatures of life, and possibly fossilized
bacteria.
A cheap, robotic foray such as the European Space Agency's SMART-1 mission,
due for launch in 2003, "could achieve tonnes of great science", says
Armstrong.
Rocks would have hit the moon at very high speeds, and fragments larger than
a grain of sand would be rare, comments Phil Bland, who studies meteorites
at Imperial College, London.
But the material would undoubtedly be there. "It's certainly worth a go,"
Bland says. "You can get a hell of a lot of information from even a
one-millimetre grain of stuff."
The form of carbon found in the Earth fragments would indicate whether they
once hosted early life, says Bland.
References
Armstrong, J. C., Wells, L. E. & Gonzalez, G. Rummaging through Earth's
attic for remains of ancient life. Icarus, 160, 183 - 196, (2002). |Article|
� Nature News Service / Macmillan Magazines Ltd 2002
Scientists debate the existence of intelligent life beyond Cambridge
By Jascha Hoffman, 11/3/2002
HERE ARE ABOUT 100 billion galaxies in the observable universe, each with
hundreds of billions of stars. What are the chances that there's any
interesting life out there?
In 1961, astronomer Frank Drake proposed a simple answer: We can assume that
some stars have planets, some planets host single-celled life forms, some of
those life forms survive to develop intelligence, and some intelligent
beings leave an electromagnetic trace before they expire.
Carl Sagan once estimated that in the Milky Way alone there must be over a
million detectable civilizations. Today, Drake sticks to his original
estimate of 10,000.
Peter Ward is sick of these loose overestimates. ''You can't turn on the TV
without seeing aliens,'' the co-author of ''Rare Earth: Why Complex Life is
Uncommon in the Universe'' (Copernicus Books, 2000) complained to a
Cambridge auditorium packed with astronomers, UFO enthusiasts, and other
onlookers last week. Ward was facing off against Harvard paleontologist
Charles Marshall at a debate hosted by the Harvard-Smithsonian Center for
Astrophysics. In 1996, Ward and Marshall worked together on a paper arguing
that a major drop in sea level, in addition to the infamous asteroid, had
wiped out the dinosaurs. But when it comes to the distribution of
intelligent life in the universe, they couldn't agree less.
"Maybe I shouldn't count myself as intelligent life," quipped Ward, a
professor of geology at the University of Washington. ''The first stop on my
book tour was a science fiction convention. A little girl told me I was the
devil for taking the aliens away.'' The Australia-born Marshall, for his
part, retains the taste for discovery that propelled him from childhood
dino-mania to a career in evolutionary biology. ''Life is capable of more
trajectories than physics or astronomy might predict,'' he said. ''I don't
know if life is teeming out there. But it could be.''
Ward and Marshall agree that the universe is full of microbes. Recent
studies have shown that interstellar clouds can generate amino acids, the
building blocks of proteins. Meteors falling to earth usually contain a
variety of organic compounds. And cells can survive under extremes of
temperature, pressure, and pH, and may be able to travel from planet to
planet on comets.
But to flourish, even simple life needs liquid water, and this limits it to
planets in the habitable zone: far enough from a star not to be boiling, but
close enough not to be freezing. And to get complex life - anything more
intricate than a flatworm - it seems that you need, first of all, a decent
atmosphere.
Here on Earth, it took 3 billion years of steady temperatures to build up
enough oxygen to support animals. The fact that our planet lies in a
habitable zone does not itself guarantee such steadiness. Ward thinks that
plate tectonics also do us a great service: When one plate slides under
another, an updraft of magma brings carbon dioxide to the surface,
eventually warming up the atmosphere through the greenhouse effect. But once
the atmosphere gets warmer, excess carbon dioxide is removed by the calcium
in the magma, and it gets cooler again. ''For billions of years, we've been
bouncing around in a very fine temperature range because of the thermostat
of plate tectonics,'' he said. ''How common is that in the universe? We
don't know.''
To survive long enough to evolve any complexity, Ward went on, life must
also avoid being destroyed by space debris. Earth is shielded by Jupiter's
gravitational field, which slows down incoming comets. But in most solar
systems, a Jupiter-sized planet has such an erratic orbit that it will
eventually fling any nearby planet away from the star. We may be uniquely
lucky to live in such a safe neighborhood.
Marshall is unimpressed by scenarios that emphasize life's fragility. "The
question is, how hard is it to sterilize a planet?" he asked. In the total
devastation following the Mount Saint Helens eruption, biologists were
staggered to find plants protected by animals that fell on them. Even at
Hiroshima, a few people survived at close range to the explosion. ''We
should expect such surprises,'' said Marshall. ''Life will find a way.''
Life also makes its own way. Take the Cambrian explosion of 445 million
years ago, when a host of scuttling sea creatures burst into a world that
hadn't seen much more than worms. What accounts for such rapid evolutionary
change? ''If you have a bunch of plant life, and someone is able to develop
a few genes for jaws, then everyone had better watch out,'' said Marshall.
It's no surprise that eyes and legs, crucial for hiding from predators,
appeared at the same time. ''With an increase in selective pressures,
complexity is bound to arise. You don't need special conditions.''
But Peter Ward was not convinced. ''If complexity is inevitable, then what
was going on for the three billion years between the first cell and the
Cambrian explosion?'' Just a slow and steady buildup of oxygen due to the
presence of simple life-forms and liquid water. ''Without the thermostat of
plate tectonics, the right conditions just don't last very long,'' he said.
Of course, there may be more to life than what we can guess now. ''We have
some idea of what conditions were necessary for us to evolve,'' Marshall
said, ''but we don't know if they're the only possible ones.'' While Ward
prefers to limit the discussion to life as we know it - carbon-based
organisms with DNA - Marshall thinks we should expect the unexpected.
Some audience members found this approach a bit too vague. ''One data point
is better than none,'' one said. ''Can you quantify the problem?''
Many scientists are working on it. Astrobiology, defined broadly as the
study of life in the universe, is now serious science. NASA and the National
Science Foundation invest tens of millions of dollars every year in it.
Astronomers search for new planets, geologists prospect for evidence of
water on already known planets, and biochemists piece together the origins
of life on earth. Still, it's mostly theory for now. And hitchhiking to the
nearest star still takes 300,000 years.
''The fact that neither of us has any numbers, shows that we're going on
next to nothing,'' said Marshall. ''But my sense of faith is that the
universe is so unimaginably rich that it will turn out that life is common,
and that scientific reasoning, while powerful, can lock us into a narrow
view of what is possible.''
Jascha Hoffman is a writer based in Boston
This story ran on page D1 of the Boston Globe on 11/3/2002.
Copyright 2002, The Boston Globe
=============
(8) MOON MIGHT REVEAL FIRST LIFE ON EARTH
From Nature Science Update, 2 November 2002
http://www.nature.com/nsu/021028/021028-13.html
Lunar rocks retain memories long since lost down here.
TOM CLARKE
The surface of the moon is spattered with over 8 million tonnes of the
Earth, astronomers have estimated. A mission to collect and study this
planetary shrapnel could provide unique insights into the origins of life
and the planets, they say1.
Asteroids and comets have pelted the Earth, Mars and Venus since the Solar
System formed. The barrage peaked during a period known as the Late Heavy
Bombardment, around 3.9 billion years ago.
The moon "witnessed and recorded all this", says John Armstrong of the
University of Washington, Seattle. Our companion formed in a massive
collision between the Earth and a Mars-sized object around 4.5 billion years
ago.
Armstrong and his colleagues estimated the impacts on the Earth by measuring
the number and size of craters on the Moon. They then calculated how much of
the Earth these collisions would have hurled into space, and the probability
that this rubble hit the Moon.
A 100-square-kilometre patch of the Moon contains about 20 tonnes of Earth
fragments, the team reckons. The same area contains around 180 kilograms of
Mars and 80 of Venus.
Collecting pieces of the three planets would let us compare their origins.
"It could end all the speculation about what the early planets were like,"
says Armstrong.
Reach for the Moon
The origins of life on Earth are hotly debated, partly because there are no
rocks older than about 3.8 billion years. Erosion and continental drift have
wiped the slate clean over and over.
But the Moon has remained largely untouched - except by asteroids - since it
formed. Pieces of the Earth littering its surface would be of all ages,
although most would date from the Late Heavy Bombardment, says Armstrong.
They could reveal the chemical signatures of life, and possibly fossilized
bacteria.
A cheap, robotic foray such as the European Space Agency's SMART-1 mission,
due for launch in 2003, "could achieve tonnes of great science", says
Armstrong.
Rocks would have hit the moon at very high speeds, and fragments larger than
a grain of sand would be rare, comments Phil Bland, who studies meteorites
at Imperial College, London.
But the material would undoubtedly be there. "It's certainly worth a go,"
Bland says. "You can get a hell of a lot of information from even a
one-millimetre grain of stuff."
The form of carbon found in the Earth fragments would indicate whether they
once hosted early life, says Bland.
References
Armstrong, J. C., Wells, L. E. & Gonzalez, G. Rummaging through Earth's
attic for remains of ancient life. Icarus, 160, 183 - 196, (2002). |Article|
� Nature News Service / Macmillan Magazines Ltd 2002
