An Overview of Mars
Let’s talk Mars.
First of all, it is gorgeous. The reason for its nickname, "The Red Planet," is obvious here. Although, I'd argue it's an orange planet but it’s not really my place. So it's the orangey-red planet. Moving on.
What is that massive scar in the middle of the photo, you ask?! Only the largest canyon in the freaking Solar System!
Behold, Valles Marineris, a canyon stretching 3000 km at depths of up to 8 km at most. For reference, the Grand Canyon is 800 km long and 1.8 km deep. “Grand” Canyon… more like the Lame Canyon, right?
It's pretty incredible that Mars is the host of the largest canyon in the Solar System because The Red Planet itself is by no means "large." Mars is about 1/3 the size of Earth.
Adorable. Our little mini-me neighbor (how very anthropocentric of me).
You might know that Earth's seasons are driven by its axial tilt (23.5 degrees). Mars' seasons are similarly driven by its axial tilt (25 degrees) and, like Earth, we suspect the degree of tilt has changed over many millennia. There's evidence Mars' axial tilt reached nearly 90 degrees at one point, but more research is needed to confirm this.
Somewhat similar to Earth is Mars' diurnal cycle and orbit. One day on Mars is 24 hours and 37 minutes (Earth hours and minutes). We call a Mars day a "Sol" so 24:37 is the length of one Martian Sol (one full rotation of the planet around its axis). Mars' orbit is also far more elliptical than Earth's, meaning it is less-circular and more oval-like than Earth's.
One year on Earth is 365.25 Earth Days (hence why we have a leap year every four years) and one year on Mars is 687 Earth Days. That's nearly two Earth Years long! To sum this up…
1.88 Earth years = 1 Mars year
687 Earth days = Mars year
One Mars year = 668.59 Sols
One Sol = 1.03 Earth days
The more dramatic, elliptical orbit of Mars means it experiences more extreme differences in seasonal pressure, temperature, surface heating, etc. than it would with a perfectly circular orbit.
The main constituent of Earth's atmosphere is Nitrogen.
If you take one thing from this post, let it be that Earth's main atmospheric gas is Nitrogen.
Earth is 78.09% Nitrogen, 20.95% Oxygen, 0.92% Argon, and 0.038% Carbon Dioxide. That last gas is the concerning one as it should be because a little Carbon Dioxide goes a long way when it comes to changing a planet as we’ll discuss.
Mars, by comparison, has an atmosphere that is 1.89% Nitrogen, 0.145% Oxygen, 1.93% Argon, and...
...wait for it...
... 96% Carbon Dioxide.
Yes, 96% Carbon Dioxide. But didn't I just say Carbon Dioxide was a problem? Aren’t we planning on sending people to Mars? Yes, I did say that and YES, some people want to go to Mars! I, personally, do not want to go. But I’m happy to work on sending other people there. Mars' atmosphere has 2461.5x more Carbon Dioxide than Earth's atmosphere but Mars is not a hot planet. In fact, it’s a very cool -80 degrees F on average.
How can that be? Well, increasing CO2 can go two ways: it can cause extreme heating or extreme cooling. Venus is an example of a runaway greenhouse gas planet and it is hot there. There are lots of reasons for this:
Venus is closer to the Sun than both Mars and Earth
Mars has hardly any atmosphere at all - it's very, very thin - so there isn't much heat retained by the greenhouse effect on Mars. CO2 molecules are spread out allowing IR radiation to escape into space.
Venus has a super-dense atmosphere that is excellent at trapping heat.
There's more to all of this, but those are a few of the big explanations.
Mars' atmospheric pressure averages around 6.0 millibars (mb), whereas Earth hovers at 1013.25 mb, about 1,000x greater than Mars. Like I said, Mars has a thin atmosphere. This causes another big problem for human missions: radiation exposure. NASA is working on making spacesuits that can withstand this kind of stress.
Last point on Mars' atmosphere: it's beautiful.
I mean, it's not even orange all the time! It'll remind you of homein 50 years when you're vacationing at Valles Marineris.
The peak you can see in the daytime photo is Mount Sharp which is a mountain in the middle of Gale Crater, a crater near the equator of Mars. This is the location of the Curiosity Mars Rover and is one focal point of my research. The mission of Curiosity is primarily to determine whether there could've been life on Mars in the past. I use Curiosity's REMS station for meteorological data, but Curiosity has "mini-labs" installed than also analyze samples of Mars' surface for evidence of life! Gale is thought to have been home to some kind of lake in the past. It could've been a frozen lake or a liquid lake, there are arguments for both of these cases.
Also of importance to my research is the South Polar Residual Cap on Mars. It's a feature we've known about since 1966 when Leighton & Murray argued the cap to be predominantly CO2 ice and not water ice. It is not a feature we have not been able to study much until the 21st century with the launch of the Mars Reconnaissance Orbiter. Since the early 2000's, speculations on the lifespan of this ice and its future have been debated.
Like the name implies, this ice cap is a perennial one (it exists year-round). It is comprised of Carbon Dioxide ice that you can see on the top as well as water ice you can't see beneath the surface. In southern-hemisphere winter, CO2 deposits on to the cap creating a large winter ice cap that reaches up to 40 degrees latitude! That's about half of the entire southern hemisphere covered in ice yearly.
This ice cap is largely a mystery. It "shouldn't" exist permanently given the pressures and temperatures at this area in southern hemisphere summer. In theory, it should sublimate away and yet, it persists. My research looks at whether or not this residual cap is growing in size (i.e. not the seasonal deposits, the permanent one you see here).
More on my research is available in another post because this post is about Mars itself. There's so much more to be said about the beloved Red Planet, but it'll have to wait for another post. We'll be digging into the mysteries of Mars' largest mountains and unique landscapes that contribute to atmospheric dynamics on the Red Planet.