Life is a mysterious thing.
As far as we are currently aware, Earth is the only place in the universe where life
exists.
Life is so prevalent on Earth because of a combination of many factors, including Earth’s
distance from its star.
It is situated in the solar system’s “goldilocks zone”, in a region that is not too hot or
too cold.
We also have a magnetic field that protects us from solar and cosmic particles.
We have an oxygen rich atmosphere which we can breathe.
We also have an abundance of water on the surface.
These and a few other factors combined allow life to exist as it does here.
But a quick look around the solar system reveals nothing on the surface of any celestial body
that is even close to resemble the green and blue lush surface of Earth!
So does this mean there is no life in the solar system?
Well the simple answer is we don’t know.
But there are a few places we are still interested in checking out, just to be sure.
I’m Alex McColgan and you are watching Astrum, and together we will travel through the solar
system and see where the most likely places to find life could be.
Here’s our Sun.
It is a very nice and stable type of star known as a G-Type main sequence star.
Not a good place to look for life as far as we know though, certainly nothing like life
on Earth could survive the thousands on degrees temperature on the surface.
We would have to expand our concepts of what life could be, perhaps beings of energy rather
than traditional elements.
Neil deGrasse Tyson, said he wasn’t opposed to the idea.
I don't see why not.
Except, um by the way, mass is energy, energy is mass.
So I can imagine an alien species that is energy. I can imagine it.
I can allow my brain to accept the possibility.
However, the possibly is extremely remote.
So I think we can leave the Sun and move on to Mercury.
Mercury does not tick many boxes in regards to what would be needed for life to form.
It has a very tenuous atmosphere, and is far too close to the Sun.
This combination means that temperatures on the day side rise to over 400c, and the night
side can drop as low as minus 170c.
It has been discovered that Mercury was geologically active in the past, but the last eruption
was thought to be one billion years ago.
Many extinction events would have happened during Mercury’s history that would most
likely have prevented life from getting anywhere.
There is water ice to be found in the permanently dark craters around the planet’s poles,
but we theorise that only liquid water can support life.
Mercury seems to be a dead, inactive and sterile planet.
The next place to visit is Venus.
Venus does have a rather substantial atmosphere, but the problem is that it still isn’t quite
far enough away from the Sun to be in the “goldilocks zone”.
On Venus’ surface, it is even hotter than Mercury, well over 400c all over the planet.
This is due to the greenhouse gasses in the atmosphere, carbon dioxide making up 96% of
it.
This heat means that water could not stay in liquid form on the surface.
There is a slight possibility, however, that there could be some form of microorganisms
high in the clouds of Venus that would use UV light from the Sun as an energy source.
The temperature and pressure high in the atmosphere is much more hospitable than on the surface,
so this possibility exists.
Moving on, one of the best bets in the solar system is Mars.
It is situated nicely in the goldilocks zone, and has an atmosphere.
The big problem with Mars though is its lack of a magnetic field.
The magnetic field on Earth prevents the solar wind from the Sun stripping away the particles
in the upper atmosphere.
Because Mars doesn’t have this, its atmosphere has been stripped of all but the heaviest
molecules, consisting of 96% carbon dioxide.
At one point in its history it did have surface water, as can be evidenced by dried up rivers
and lake beds.
However, today that water has gone and if there was any life on the surface, this has
most likely gone too.
Scientists have been keen to find evidence in rocks with the Viking missions and looking
for methane in the atmosphere with the rovers currently on the planet, but they have so
far found only traces of evidence.
But NASA are not deterred, finding solid evidence of life on Mars is now one of their primary
objectives, so they clearly think there is still a good chance of finding something.
There are a few tell-tale signs that life could have existed or still does on Mars.
There are possible bio signatures like methane in the atmosphere, often the by-product of
life.
Scientists can’t quite agree on where the quantity of methane gas comes from, and life
is a definite possibility.
We also have 34 meteorites which originated from Mars.
These are highly valuable as they are the only samples from Mars that we possess.
A few of these meteorites even contain what looks to be fossilised bacteria, although
they are much smaller formations than any terrestrial bacteria on Earth.
This is not conclusive evidence however, as even these formations can be explained by
natural processes.
At this point in time, there are a couple of possible places to find life on Mars.
One would be about 10 meters under the surface.
Water can be in liquid form this far down, and any life would be much more protected
from cosmic and UV radiation.
Another theory is that microorganisms could exist under the polar ice caps.
Potential evidence of this could be the darkening of these spider patterns next to geysers on
the poles.
The darkening could be these microorganisms
as they photosynthesis the Sun's UV light from under the surface.
With all the attention Mars is getting from the global scientific community, I would guess
we will know conclusively whether there is life on Mars within the next 30 years.
The possibility of life outside of Earth opens up a host of possibilities and interesting
thought experiments about the cosmos.
Brilliant.org has an astronomy course specifically about ‘Worlds beyond Earth’, where you
can actively grapple with puzzles and problem solving around the goldilocks zone I mentioned
in this video, how we can discover exoplanets around other stars, and a host of other thought
provoking questions.
My videos tend to explain the facts about space, but Brilliant.org teaches ‘how’
we know these facts are true, using maths and physics.
By actively engaging with problem solving around this topic, you will gain a much deeper
understanding of what you see in my videos.
which is why they are a great fit for you.
If you go to brilliant.org/Astrum, you can sign up for free to have a sample of their
courses, and by using that link, the first 200 people will get 20% off the annual Brilliant
premium subscription.
That's the subscription I've been using.
And there we have all the terrestrial planets.
Next time we will look at the outer solar system and see the potential places for life
there.
If you enjoyed the video, like and share as it really helps me to make more videos in
the future.
And finally, check the comments for a little update from myself.
Thanks, and see you next time!