This is an update in my continuing coverage of the
intriguing star system called TRAPPIST - 1 that includes no less than seven
earth-like rocky planets, see my first video update on that on this channel for
the back story. In the few days since NASA's press conference, a clearer
picture is emerging on just how bizarre yet familiar this star system is.
There seems to be a high likelihood for liquid water
existing on two of these worlds, and in fact could exist on all seven if the
atmospheric conditions of some of those worlds allow it. But there is actually
a very specific reason why scientists think this is likely.
When planets form out of the discs of debris that often
surround young stars, the materials in the disc are not uniformly distributed.
You can infer just where a planet originally formed by its composition. In
early solar systems planets tend to migrate until they ultimately settle into
stable orbits. The current models for TRAPPIST - 1 indicate that the planets of
the system formed relatively far out from the star and eventually migrated
inward. This would mean that they formed in an area of the disc that was rich
in water ice. Warm water ice up, and you have liquid water.
Where you have liquid water, you have the potential for
life. Now one point against TRAPPIST - 1's planets developing life is their
proximity to the star. They are really close and when you're close to a star
you are subject to some serious radiation. One type of radiation that's
unfriendly towards life is ultra-violet. Here on earth we are protected from
the sun's UV radiation by the ozone layer. A similar such ozone layer may
protect one or more of the worlds at TRAPPIST - 1, only further study will
tell.
Another issue is the presence of a strong magnetic field to
deflect radiation. These planets would need that to support life, but as with
Earth, it has a strong magnetic field so they may too. Again, further study
here is needed.
But in one area the new planets are favored for life. Life
here is linked to tidal pools early in earth's history where the magic of
organic chemistry could be worked that eventually leads to life. For life to
develop, at least according to current thinking, you need tidal pools. Tidal
pools need tides. Tides require a moon. Now, at first glance the mechanics of
the TRAPPIST planetary system seems to disfavor moons. These planets pass very
close to each other and affect each other with their gravity and probably would
have tossed any moons out of that area pretty quickly.
But that's also the saving grace. They pass so close that
the planets themselves would create tidal effects on any water present in the
system. So here we have a case where the circumstances allow for tides without
moons.
So let's say, hypothetically, that on one of the planets
microbial life has developed. The interesting thing here is that if it has,
then at some point it is likely that life will arise on any of the other
planets in the system that allow for it. The reason for this is panspermia.
This is a process where impacts by asteroids can blow debris off of one world
where it would then wander space for a bit and land on another. It is possible
for dormant microbial life to survive the journey and in fact it's possible
that we've seen this first hand, though the subject is more hotly debated than
is commonly known.
During the Apollo 12 mission to the moon astronauts
retrieved the main camera from the surveyor 3 mission that had been sitting on
the moon for three years. When they got it back to earth, they found living
bacteria between the lenses that appear to have survived the harsh conditions
of the moon. Now, this has been widely criticized because there was apparently
plenty of opportunity for contamination but it still seems rather odd that the handful
of bacteria all happened to be the same species and when cultured behaved as
though they had been dormant. The truth will likely never be known since the
cameras are not now in a sterile environment.
This sort of thing could easily occur with rocks, and might
in fact have happened in our own solar system. One existing theory is that life
in our solar system actually originated on Mars and was deposited on this
planet by a meteorite. This theory is attractive because at the time that life
arose on earth, the environment here was not that great for the formation of
life. Mars had once been a more hospitable place for life than Earth in this
solar system.
Given the very close proximity of the planets of TRAPPIST -
1, these planets would pass by each other and look even larger in the sky than
our moon does, it seems likely that materials get exchanged, or did in the
past, due to impacts. As a result, life may have hitched a ride and populated
more than just one world in this system.
Only time will tell if these worlds at TRAPPIST - 1 hold the
potential for life or are more likely to be sterile worlds. After all, three
planets also lie within our sun's zone of habitability and any alien culture
out there studying us probably initially wondered if life could exist on all
three.
But as they study the atmospheres of our planets, they would
quickly see that the closest of the three, Venus, is unsuitable for most
straightforward kinds of life and they would see that Mars is too small to hold
the necessary atmosphere for much other than underground microbes. But then
they would see our blue jewel and the oxygen life creates in its atmosphere and
then they would know.
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