WEEK 4: OUR NEAREST NEIGHBORS IN THE SOLAR SYSTEM

This week we will talk about not only the planets Venus and Mars, but a whole host of other 'things' that share our part of the Solar System and are close enough for missions in the past and the future. It's a fascinating topic and you could spend HOURS just thinking about all the places we could send spacecraft.
Let's start with EARTH'S FIRST TROJAN ASTEROID discovered last year.
Don't worry, it will never hit the Earth. It's in a strange gravitational part of our orbit called a Lagrange Point.

http://www.nasa.gov/multimedia/videogallery/index.html?media_id=103550791

PART 1: VENUS vs MARS

Venus has an atmosphere, has about the same gravity, and is not that far from our planet. Yet, we could really never send people there to explore the surface. Why?

Give 5 reasons.

JAXA, the Japanese Space Program (yes, we're not the only ones!) have studied this planet extensively. Here's one of their orbital spacecraft.

Mars is our other planetary neighbor. Unlike Venus, Mars has great potential for manned flights in the future. It's cold and dusty, but nothing like Venus. The atmosphere is thin and we're not sure where to find water, so be sure and take air and water along for the trip.

It will take 3 months (not weeks) to get there!

What do you think the gravity will be like?

Notice that we've skipped discussing our Moon. That's because we'll spend an entire lesson (next week) just talking about our missions there.

Beyond Mars is the Asteroid Belt, and if you are feeling a bit brave, you could decide to send a spacecraft all the way to the largest member, Ceres. Ceres is about the size of Texas if you wrapped it in a sphere.

Shown above is the best image of Ceres pictured there below the Moon.

Does it have gravity? What do you think?

If you jumped, would you land back on the surface or just float off into space?

So, how many asteroids are out there? Are there any close to Earth?

WOULD YOU LIKE TO SEE ALL THE ASTEROIDS ON ONE MAP?

YIPES! That's a lot. Let's count them.

Trojan asteroids are by far the strangest. They stay well ahead or behind the planet they are near and have a unique orbit. The green lines show this orbit.

NASA keeps up with every asteroid near us in a program that you can see at the JPL website. Asteroids like these are called Near Earth Objects (NEOs).

One turned out to be a piece of a lost spacecraft!

Space junk is an entirely different topic and we'll get to that when we cover satellites.

This giant flying potato is called EROS and we've sent a spacecraft there!

JPL web link:

http://neo.jpl.nasa.gov/missions/