Wednesday, August 13, 2014

Getting High On Life

Biology concepts – bacteria, climate, respiratory, birds, arthropods, astrobiology, clouds

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.
The astrophysicist Carl Sagan said, “There are naive questions, tedious questions, ill-phrased questions, questions put after inadequate self-criticism. But every question is a cry to understand the world. There is no such thing as a dumb question.” A cry to understand the world – so keep asking the questions, even if they seem silly.

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.

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.
We don’t know how often the vultures venture that high, but the bar headed goose (Anser indicus) makes a habit of flying over Mt. Everest. This is a migratory bird that flies over the Himalayas twice a year, sustaining 8-hr flights at more than 28,000-29,000+ feet (8.8 km).

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.

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.
But we shouldn’t restrict our discussion to birds, there may be other things that get high (pun intended). The winds can help out. Some small arthropods disperse themselves as youngsters by ballooning with silk. Spiderlings (newly hatched spiders) risk being eaten by siblings if they hang around after hatching, and too many spiders in one area makes it hard to find food, so they get as high as they can and then shoot out a strand of silk.

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.

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.
The clouds are up there, could they harbor life? They contain water; life needs water. There are several types of clouds and they sit at various altitudes based on type, topping out at about 13 km (8 mi). The highest clouds are at about the same altitude that the griffon vulture has been known to fly (see picture).

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!

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.
Bacteria are particularly well suited for life in the atmosphere. There are bacteria that can withstand intense radiation, can live in extreme cold temperatures, and can live nearly without water. These sound like good candidates for something that could escape Earth altogether.

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).

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.
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.

Next week, another question with a more fascinating answer than you would expect - why is it so hard to catch or swat a fly?

Pawar SP, Dhotre DP, Shetty SA, Chowdhury SP, Chaudhari BL, & Shouche YS (2012). Genome sequence of Janibacter hoylei MTCC8307, isolated from the stratospheric air. Journal of bacteriology, 194 (23), 6629-30 PMID: 23144385
Dillon ME, & Dudley R (2014). Surpassing Mt. Everest: extreme flight performance of alpine bumble-bees. Biology letters, 10 (2) PMID: 24501268

Hawkes LA, Balachandran S, Batbayar N, Butler PJ, Chua B, Douglas DC, Frappell PB, Hou Y, Milsom WK, Newman SH, Prosser DJ, Sathiyaselvam P, Scott GR, Takekawa JY, Natsagdorj T, Wikelski M, Witt MJ, Yan B, & Bishop CM (2013). The paradox of extreme high-altitude migration in bar-headed geese Anser indicus. Proceedings. Biological sciences / The Royal Society, 280 (1750) PMID: 23118436