Jupiter, at first glance, is perhaps the last place you
would expect to find life. It's after all a roiling, hot gas giant. But it
might surprise you that the gas giant itself has, at least in the past, been considered
a possible home for life. And not just microbial life, but complex life. And
while it's a long shot, it's not ruled out that something could inhabit the
upper reaches of its atmosphere.
Jupiter is a generally misunderstood world. It's usually
thought of as a huge ball of gas. But in reality, it's much more complicated
than that. If you descend into Jupiter's atmosphere, you will first find a
turbulent upper layer made up of a mix of gases, mostly hydrogen and helium.
The further you go down, the hotter it will get due to the high pressures of
the interior. At about 1000 kilometers below the top of the cloud deck you transition
to one of the stranger natural substances thought to exist in our solar system.
You would find metallic hydrogen.
Under the extremely high pressures of Jupiter's atmosphere
hydrogen would be compressed into a soup of nuclei and electrons that exist in
an ambiguous state that wouldn't have a clear boundary between a gas and a
liquid. While metallic hydrogen is described as a liquid, it's a bit different
than any other. It's better to think of the hydrogen as simply getting denser
the deeper you go rather than use labels. Beyond that thick layer at the heart
of the planet, it's thought you would find a core.
Not a lot is known about this core, but it's probably made
of rock and metal just like the inner planets. It's not yet known if it's solid
or completely molten or some mix of the two. Planetary cores are generally hard
to study, and Jupiter's is among the hardest. But how could such an alien and
strange environment such as Jupiter support any kind of life? The answer is in
the conditions of the upper atmosphere.
In 1976, Carl Sagan and Edwin Salpeter released a paper,
citation in the description below, in which they suggested that ammonia-based
life of some kind might exist in the atmosphere of Jupiter. They envisioned
three hypothetical kinds of animal that might live there which they termed
sinkers, floaters and hunters. In particular, the floaters were envisioned as
enormous gas bags, perhaps kilometers across and visible from orbit that suspended
themselves in the atmosphere using helium.
Now, we have never seen floaters with any of our probes to
Jupiter and this was a very speculative paper based on thinking deriving from
what we know about our own oceans and life there. No such indications have ever
surfaced that such a thing could really exist on Jupiter. But what does exist
at Jupiter is the possibility of some interesting life related chemistry. The
chemicals in the upper atmosphere of Jupiter do include water, ammonia and
methane along with plenty of hydrogen in gas form.
These just happen to be the gases used in an interesting
experiment done in 1952 by Stanley Miller and Harold Urey. They wanted to
recreate the conditions of early earth and see if they could produce the initial
prebiotic chemical reactions that are believed to have ultimately led to the
dawn of life on earth.
What they did was pass water vapor through a mix of
hydrogen, ammonia and methane gas. They then subjected that mix to periodic
electrical discharges intended to simulate lightning. Then they looked at what
came out the other side and it was, to say the least, interesting.
They found lots of organic compounds coming out of the mix. Most
importantly, they initially found a number of the amino acids that are used by
life. In 2007, however, the original sealed samples from the experiment were
reexamined and as it turns out all 20 amino acids were present that are used by
life on earth.
Since then, numerous revisions have been made to the model
of what our planet's early atmosphere was like. As a result, a number of subsequent
experiments have been done based on the Miller-Urey work ranging from changing
the energy source to a volcano rather than lightning, adding in new chemical
mixes that more accurately resemble what the early atmosphere is thought to
have been like and so on. The results of many of these experiments has been the
creation of even more types of organic molecules than Miller and Urey's
experiment produced.
These experiments make it seem likely that at least the
basic the chemistry for life first arose on some volcanic island on Earth
billions of years ago. For Jupiter, this would be a more difficult process
though it does have extremely powerful lightning and no shortage of heat. The
problem is in its atmosphere, which is extremely violent. Gases circulate on
that world by rising in certain areas and falling in others and any kind of
life, microbial included, would have to deal with impossibly high temperatures
and pressures when circulating deep below.
As Sagan noted in a segment on this topic in his television
series Cosmos, such organisms would have to reproduce very rapidly. And while
the prospect of life living in the atmosphere of Jupiter is somewhat of a
stretch due to that roiling atmosphere, there may be gas giants and even brown
dwarves in the universe calm enough to harbor at least some form of microbial
life in their upper atmosphere, or possibly even more.
In a paper by Jack Yates and his colleagues at the University
of Edinburgh
This opens up vast new territory in the search for life in
the universe. In 2013, a brown dwarf known as WISE 0855-0714 was discovered and
seemingly has water-based clouds floating in its upper atmosphere. Using Sagan
and Salpeter's research, they applied that thinking to the brown dwarf and
concluded that yes, life might exist there.
The James Webb Space Telescope is slated to take an in-depth
look at close brown dwarves, such as WISE 0855-0714 which is only 7 light years
away. And while it's hard to envision native life having a way to evolve in the
first place in a place like Jupiter or a brown dwarf, it's been suggested that
dust floating in the atmosphere might do the trick for a solid place to do it or
even microbial life being delivered by an asteroid through panspermia.
One can imagine that this kind of inhabited gas planet might
be quite rare, but it does seem to at least be hypothetically possible and that
in the future, when we do detect evidence of life, perhaps it might come from
the spectra of a brown dwarf's atmosphere. But I'm left with one lingering,
highly speculative thought after making this video. If Jupiter, then why not
Saturn?
Thanks for listening! I am futurist and science fiction
author John Michael Godier currently probably sounding a bit scratchy because
it's spring and my allergies are working overtime and be sure to check out my
books at your favorite online book retailer and subscribe to my channel for
regular, in-depth explorations into the interesting, weird and unknown aspects
of this amazing universe in which we live.
No comments:
Post a Comment