Snowball Earth: Mission to Planet Earth in the Distant Past
In this class, we've learned about our planet, the Earth, and about many other planetary bodies in our solar system. We've seen that there are many interesting similarities and differences between them. The Earth resides in the warm inner solar system, near the Sun, but Venus and Mercury are even hotter than the Earth. Most of the solar system is farther from the Sun than the Earth is, so we've learned about things like ice on Mars, on Europa, on Enceladus, etc..., and even about signs of liquid water beneath the surfaces of some of those bodies.
Please read this carefully!
For this question, you're going to imagine you're a space alien living about 650 million years ago, on some other planetary body (like Mars or a moon of an outer planet), and you're studying the Earth.
Let's imagine this alien species has evolved much like humans have, and has senses similar to ours, and a level of intelligence like ours, and has developed science much like we have today. So there you are - it's about 650 million years ago, and you're a space alien with human-like senses and intelligence, and a level of scientific and technological development like early 21st-century humans have. Just because you're a space alien, it doesn't mean you have super-duper advanced technology. You've got late-20th to early-21st century technology, if we're making a comparison to humans. Now, here's the thing - 650 million years ago, the Earth was weird! It was going through a strange episode in its history called Snowball Earth. (In fact, there were more than one of these "snowball" episodes. The most recent one was about 650 million years ago. Complex multicellular life evolved on Earth about 540 million years ago. Scientists aren't sure if the Earth totally froze, with the oceans and continents completely covered with ice, but let's assume it did. Nothing but white everywhere. Like the ice planet Hoth from "The Empire Strikes Back". Kind of like the illustration in this article about Snowball Earth
Now think about your alien species, as that species invents astronomy. You'll have seen the Earth in the sky. It's really bright white, very reflective. Through telescopes, you can see the surface. You can tell it's not just a cloud layer, like Venus - the surface is covered in bright white ice.This planet is totally made of ice!, you might say. How can a ball of pure solid ice exist so close to the Sun, and without a lot of reflective clouds to shield it from the Sun's energy??
Answer this question: How could your alien species figure out that the Earth ISN'T simply a ball of pure ice?
How could you figure out that the Earth is mostly NOT ice? It's mostly rock, and even has metal (an iron core) in it. This is true now, and it was true 650 million years ago. At that time the Earth merely had a layer of ice on its surface.
Write a short written answer explaining how you could figure this out.
Please try to include method 1 to give the best explanation.
Method 1 - To get MOST of the possible points
If you want to get about 3/4 of the possible points, think of the ancient Earth the way we think of Mars or Europa or Enceladus today. It's an object to be explored with early-21st-century telescopes and early-21st-century spacecraft. What would be the space missions you'd propose, and which you'd ask your government to fund?
Don't forget! - Your politicians don't like spending money on space any more than ours do. Remember what Neil DeGrasse Tyson said in his book Space Chronicles:
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