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Carl
Sagan wasn’t just the host of the original Cosmos
on TV.
He
solved the riddles of Venus’ high temperature, the seasons
on
Mars, and the color of Titan. He also wrote one of my
favorite
speculative fiction novels, Contact.
The movie is
good;
the book is better.
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Today’s question might seem a little naive – Is there any life that could escape Earth?
But I assure you, there’s more to it than you might think – and no, the answer
isn’t an astronaut. Let’s put it another way - is there any living organism that
could get high enough on its own to leave our atmosphere?
Well, I guess the first prerequisite for escaping our
atmosphere would be an organism that could get really, really high. Some birds
can fly at absurd altitudes.
The Ruppell’s Griffon Vulture (Gyps rueppellii) has the highest recorded flight. On
November 29, 1975, a Ruppell’s vulture was sucked into the jet engine of a
plane flying at 39,700 ft (12.1 km, Mt. Everest is 9.0 km) over the Ivory Coast
in Africa. A unfortunate flight plan for the bird, but amazingly the plane landed
safely after ingesting a bird with a 10-foot wingspan.
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These
two pictures are not at the same scale. The Ruppell’s
vulture
on the left has a wing span of about 10 ft (3 m),
while
the bar headed goose on the right (see the bars?) has
a
span of about half that. They should not box one another,
it’s
be a slaughter. But still, these are both much bigger than
most
birds. Is their longer wing span part of their success at
high
altitudes? Songbirds rarely fly above 2000 feet.
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The real question is why birds would fly so high. As you
ascend, the air becomes thinner; fewer molecules make the atmosphere less
dense. Since bird flight is basically supported by the air, thinner air makes flying
much more difficult.
Difficult flying means that more energy is required. Birds
live right on the edge of oxygen debt all the time; flying is tough at any
altitude. But high in the air, it becomes even harder and requires more energy.
And what’s needed to make energy in the form of ATP – oxygen (see this post) –
the very thing there is less of at high altitude.
The bar headed goose and his compatriot avians breaks some rules in
order to become a high flier. Birds in general are better at oxygenating their
muscles, because they can exchange oxygen for carbon dioxide on both their
inhalation and their exhalation (this will be the focus of s series soon). But that
isn’t all.
Birds can also pant better than mammals. Panting is way to
get more oxygen to the muscles, but it comes at a cost - it brings blood vessel
constriction in the brain (an attempt to prevent oxidative damage). This makes for poor
control, focus and decision making. But birds can pant much longer and
harder without constricting brain vessels, so they don’t make stupid decisions - birds aren't bird brained.
Bar headed geese go even further (a 2013 study). The blood
vessels in their muscles penetrate deeper and are more extensive. This can
supercharge their muscles with oxygen so they can make more ATP and flap more
energetically. Finally, the hemoglobin (oxygen-carrying molecule) of bar headed
goose red blood cells is slightly different than that of other birds. It grabs
onto oxygen molecules easier and quicker, so it does a better job of
transporting the maximum amount of oxygen to the muscles.
We humans may not want to flap at high altitudes, but we
could learn a lot from the bar headed goose about maximizing oxygen
utilization. That’s where we get most of our best ideas – we steal them from
nature’s rule breakers.
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Many
species of spiders, mites, and small caterpillars use
kiting
as a means of dispersal. Remember that these are
newborns,
and are usually of the smaller species, so these
fellows
are awfully small. That makes it possible for a breeze
to
catch the silk they spin straight up into the air and carry
them
off to new neighborhoods. This is thought to be one of
the
primary ways arthropods colonize newly formed islands.
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The wind picks up the youngsters and deposits them somewhere
else. However, the wind sometimes doesn’t want to let them go. They've been
know to travel into the jet stream, and have been noted living in weather balloons
at more than 16,000 ft (4.9 km).
Bees too have been found on the slopes of Mt. Everest (5.6
km). A 2014 study says bees could theoretically fly at almost 30,000 ft.; they could look
down at Mt. Everest if they chose to. The researchers reduced the density of air and the oxygen
concentration to match what would be found on top of the world and the bees
flew just fine. They compensated not by beating their wings faster, but by widening
and lengthening their stroke. Pretty good for an organism that many mistakenly
believe shouldn’t be able to fly at all. But just because they could fly at
that altitude, doesn’t mean that they do.
For one thing, bees and other arthropods go dormant when
temperatures dip into the 40’s ˚F (7-10˚C) they become immobile and if they
stay that way, they die. Not a good candidate for escaping Earth, where the
temperature approaches -40˚C as you travel through the clouds.
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These
are the major types of clouds and their average altitudes.
They
carry dust, water, chemicals, and apparently a whole lot of
bacteria
and fungi. The 2013 paper says the bacteria act as seeds
for
cloud formation and can therefore affect the weather.
Powerful
beings.
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Do all clouds have a living lining? You betcha. A 2013 study
has shown that the clouds are actually their own biological environment.
Bacteria, some from the ground, some from the ocean, and perhaps some from the
air, are living and dividing up in the clouds. The study sampled air at 10,000
feet and found that air over water, had more marine organisms, while air over
land had more soil organisms. They also found that hurricane air had many more
organisms, so they hypothesize that strong winds pull up more organisms into
the upper atmosphere.
But wait you say, the vulture was at 39,000 feet, and these
bacteria were only at 10,000 ft. Well, let’s go higher. A 2009 study from India
showed that microbes were living as high as 25 miles (41 km) in the
stratosphere. This shames the vulture and he makes him feel inadequate. What’s more, the
2009 study found three strains of bacteria in the clouds that are not found on the surface of
the Earth!
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Meteorites
are one way that life might travel from planet to
planet.
The organisms would have to survive the jolt that
speeds
them to escape speed (bacteria can), and they have to
survive
the temperatures of reentry. Interestingly, studies
show
that even though the surface of a meteor entering the
atmosphere
is several thousand degrees, it feels like a warm
summer
day just a few centimeters deeper.
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A 2012 draft genome of one of these bacteria, Janibacter hoylei, confirms that it is
different from any organism found previously on Earth. These bugs might be
living their entire existences in the upper reaches of the atmosphere.
But we could look at this from the other direction as well.
Could J. hoylei have come from
space and is just living in the clouds because it liked the first place it saw
when it got here? Astrobiologists are excited to study these high altitude
bacteria in terms of whether they could seed other planets or whether life
could come here from other places.
The hiccup in all our hypothetical space entering organisms is something called escape speed.
In order to leave Earth’s gravitational pull, an object on the ground must
travel at 11.2 km/sec. The escape speed decreases as you travel away from the
center of mass, but even at 9000 km, an object must travel at 7.1
km/sec. A bullet fired from a rifle travels at about 1.7 km/sec, so you get the
idea. It ain’t easy to leave Earth behind, even if you happen to be rugged
enough to survive space (as some bacteria and lichens can, see this post and this post).
One theory holds that bacteria living in the
high atmosphere could be affected by the magnetic field lines of the Earth and
sort of ride along a magnetic railway. Tom Dehel, an electrical engineer for
the FAA, proposed in 2006 that electromagnetic fluxes, like the solar flares
and fields that produce the auroras in the northern and southern hemispheres,
could provide charged bacteria with enough energy that they could escape
Earth’s gravitational pull. Not one scientist I could find has signed on to
this idea. But still, there are no silly hypotheses, they’re all just a cry for the
truth.
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The
Earth’s magnetic field protects life on the planet from many
types
of deadly radiation. Near the poles, the earth’s magnetic field
lines
bend to pass through the center of the planet. It is here at the
poles
that the radiation can interact with the field lines in a position
for
us to see. These are the Northern and Southern Lights.
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Next week, another question with a more fascinating answer
than you would expect - why is it so hard to catch or swat a fly?
Dillon ME, & Dudley R (2014). Surpassing Mt. Everest: extreme flight performance of alpine bumble-bees. Biology letters, 10 (2) PMID: 24501268
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