The Mystery of Mars

**SPEAKER_2** (0:08)
You're listening to Strange by Nature, your guide to the strange, weird, unbelievable and improbable wonders of the natural world.

**Kirk Mona** (0:23)
Hello, everyone, and thanks for being here today. I'm Kirk Mona, and joining me are Rachel Gimza and Victoria Thompson. We're all naturalists who together have scoured the world for weird and wonderful wonders, just to please your mammalian brain's desire for novelty. Isn't that nice? Let's do this.

**Victoria Thompson** (0:43)
Well, hello, everybody. Welcome to the show. We are all here again this week. It's so good to be with you.

**Kirk Mona** (0:48)
Yes, it is wonderful to be here once again.

**Rachel Gimza** (0:53)
I even have him in my actual new recording studio space.

**Victoria Thompson** (0:59)
Lovely. It's great. It's very exciting. Well, I start things off this week, and it's kind of a little bit of a Kirk topic, I want to say.

**Kirk Mona** (1:10)
Interested?

**Rachel Gimza** (1:12)
Color me intrigued.

**Victoria Thompson** (1:13)
Okay. Well, all right.
I'm going to start off by my section by saying Mars is a problem. Mars is a problem.

**Rachel Gimza** (1:25)
Mars is a problem. I mean, I'll go with that. Sure. Why is Mars a problem? Mars?

**Kirk Mona** (1:31)
Of all the chocolate companies out there, I think we need to... Oh, you mean the planet.

**Rachel Gimza** (1:38)
Oh, that's different. I got it. I got it.

**Victoria Thompson** (1:42)
Well, the reason Mars is a problem is that it is way smaller than it should be.

**Rachel Gimza** (1:48)
What?

**Victoria Thompson** (1:49)
Yeah.

**Kirk Mona** (1:50)
Okay. More interested.

**Victoria Thompson** (1:52)
Okay.

**Kirk Mona** (1:53)
Tell me more.

**Victoria Thompson** (1:53)
Models of the early solar system show that the planet in the location where Mars is should have a mass about the same as Earth's mass.
But instead, Mars has a mass of 0.107 of Earth's. So about a tenth of Earth's mass.

**Kirk Mona** (2:13)
That's not a lot, man.

**Rachel Gimza** (2:14)
Pretty small, yeah.

**Victoria Thompson** (2:15)
You know, Mars is smaller, but also Earth is actually especially dense for a planet. So.

**Kirk Mona** (2:22)
Okay.

**Rachel Gimza** (2:23)
Yeah.

**Victoria Thompson** (2:24)
But it is at least 10 times too small. To understand this, we are going to have to back up a little bit and talk about a sort of common hypothesis of planet formation.

**Kirk Mona** (2:37)
Okay.

**Victoria Thompson** (2:38)
So around young stars, there's a protoplanetary disk, which is a very large disk of gas and dust.
And electrostatic and random collisions cause bits of matter to start sticking together. And they form tiny objects called planetesimals.

**Rachel Gimza** (2:57)
Okay.

**Victoria Thompson** (3:00)
This is all very simplified, of course.

**Rachel Gimza** (3:02)
Oh, so it has to be.

**Kirk Mona** (3:05)
What?

**Victoria Thompson** (3:06)
I mean, first of all, I can't understand the actual science, probably.

**Rachel Gimza** (3:12)
It's like, it's literal astrophysics.

**Victoria Thompson** (3:16)
Yeah.

**Kirk Mona** (3:17)
Stuff attracts stuff.

**Victoria Thompson** (3:18)
Yeah.

**Kirk Mona** (3:19)
There you go.

**Rachel Gimza** (3:19)
Grabbing it.

**Victoria Thompson** (3:21)
Once an object reaches about one kilometer across, it has enough of a gravitational field to start pulling stuff in that way as well. So rocky planets formed by this method closer in where there's more dust, and then a bit further out where things are colder, bits of ice also get accreted, which allows gas in the mix to kind of cool down enough to stick and create gas giants.

**Kirk Mona** (3:49)
Okay.

**Victoria Thompson** (3:49)
That's my understanding.

**Kirk Mona** (3:52)
Yeah.

**Rachel Gimza** (3:52)
Great.

**Victoria Thompson** (3:53)
Probably wrong.
But close enough. So meanwhile, there are also two opposing forces that are tugging at this material. There's the planetary wind, which is pushing gas out of the solar system, and gravity from the star pulling material back toward the center of the system.

**Rachel Gimza** (4:13)
I'm going to ask a question, and you probably won't have an answer, and it might come up later in the podcast. What is a planetary wind?

**Kirk Mona** (4:23)
I was going to ask, is that different than the solar wind?

**Victoria Thompson** (4:26)
I think it's just like a solar wind.

**Kirk Mona** (4:28)
Okay.

**Rachel Gimza** (4:29)
Okay.

**Victoria Thompson** (4:29)
I think I wrote down the wrong thing, probably. I think solar wind.

**Rachel Gimza** (4:37)
Because space is a vacuum.

**Kirk Mona** (4:40)
But it's particles escaping the sun. Got it.

**Rachel Gimza** (4:43)
We call it a wind, but it's not like air wind. It's particles floating through like wind. Got it.

**Kirk Mona** (4:50)
Fairly fast moving particles ejected from the sun.