It’s Professor Dave, let’s go to Mars.
Mars has been a source of fascination for us ever since we first began observing the sky.
It glows with a faint red hue, and for this reason, it was named after Mars, the Roman
god of war.
Though our other next door neighbor, Venus, is a bit closer, Mars is the most similar
to Earth in terms of conditions, with a snapshot taken from its surface being rather hard to
distinguish from a rocky desert here at home.
In addition, it is the only other planet that exhibits temperatures that are at certain
times within a range that would be hospitable to humans, though admittedly a bit on the
cold side.
However, there is a big difference in size, with Mars having only half the diameter and
one tenth the mass of the Earth.
Before we knew much about the planet, it was speculated that intelligent life might live
there, a notion that was elevated upon the discovery of features on the surface that
were dubbed channels by an Italian astronomer, but then misinterpreted to mean canals, implying
that they were built by sentient creatures.
Science fiction went wild with the idea of Martian beings coming here in spaceships to
take over the Earth.
But as our ability to get clear images of the Martian surface became more refined, we
began to see that it is a rather dead planet.
It has a minimal atmosphere, and is too cold for water to flow on the surface, with some
locked away in its polar ice caps, just like on Earth.
The only difference is that on Mars, these caps include quite a lot of solid carbon dioxide
in addition to water.
Other prominent surface features include Valles Marineris, a gigantic canyon five thousand
kilometers long and ten kilometers deep that would make the Grand Canyon look like a hole
in the ground.
A region called the Tharsis bulge is home to many volcanoes, one of which, Olympus Mons,
is twenty five kilometers tall, three times the height of Mount Everest, and the tallest
peak in the solar system.
Mars may resemble Earth in a lot of ways, but its atmosphere is not one of them.
Mars has an atmosphere only about one percent as thick as Earth’s, and it’s mainly carbon
dioxide, at about 95 percent.
The rest is largely nitrogen, with a little bit of oxygen and water vapor as well.
This means that there is not much of a greenhouse effect on Mars, which explains why it is so
cold, with an average temperature that is colder than it gets anywhere on Earth.
Even still, there is enough atmosphere for wind to exist, and this wind sometimes results
in dust storms that cover the planet in a pink haze.
There is no rain, however, as there is nowhere near enough water vapor for rain to occur.
Nevertheless, a variety of geological features suggest that running water once existed on
the surface of Mars.
The channels that cut through the crust are just like similar features on Earth that form
due to the slow erosion of flowing water on rock.
So in the past, Mars must have had a warmer, thicker atmosphere, more closely resembling
Earth today.
But this must have been a few billion years ago.
Looking inward to the core, we believe it is similar to that of Earth, with lots of
iron, surrounded by a mantle and then the crust.
However, Mars is so small that the core must be much cooler, with so much less pressure
crushing down around it.
This also means it is probably solid, which would explain the fact that Mars has no magnetic field.
This could also explain the lack of atmosphere, as without a magnetic field, the solar wind
may have slowly stripped the planet of any surrounding gas particles, removing any potential
greenhouse effect, and causing a runaway cooling.
Mars also has two moons, Phobos and Deimos.
These are only about twenty kilometers across, and are oddly shaped, suggesting that they
are probably asteroids that have been captured from the asteroid belt, which we will get
to later.
So what happened to Mars?
Was there once running water there, and if so, how did it become such a dry, desolate place?
We have much to learn regarding our own world by studying Mars and other planets, hopefully
learning lessons that will ensure that Earth won’t go the same way.
But before we talk about the future of Earth, let’s get through the rest of the solar system.
With the terrestrial planets wrapped up, it’s time to move on to the gas giants, so let’s
check out Jupiter next.