SPACE pt. 1 – The Terrestrial Planets

I love space. Let’s start with some YouTube videos of the Sun to get us in the mood for some SPACE

Watch the edges for brilliant solar flare action on this one:

Now that you’re ready, let’s get stuck in to the four planets closest to us, and closest to the Sun. These are known as


The Terrestrial Planets

(to scale)



Mercury is the smallest planet, and is closest to the sun. Its “day” is one-and-a-half times longer than its “year”; it turns on its axis twice by the time it’s gone around the planet three times. Since it turns so slowly, the side nearest the sun reaches over 500°C, but the side facing away is at -160°C.
Exaggerated colour image:

Craters on the surface:

Mercury passing in front of the Sun:


Venus is closest in size to Earth of all the planets, but that’s about where the similarity stops. Its atmosphere is the densest of all the planets in the solar system, comprising mainly carbon dioxide – standing at the surface would be like swimming over 1km under the sea. Since (as most of us know) CO2 traps heat, the temperature on the surface is about 460°C; sitting above the CO2 clouds are evaporated droplets of sulfuric acid, and volcanic activity is rife. A “year” is less than two days long, but the atmosphere means that temperatures are the same, all over the planet, all year long.
Venus under the clouds:

Some surface shots:


Earth, our home, is the largest of the terrestrial planets. If Earth were scaled to be the size of a bowling ball, the surface of the planet (including atmosphere!) would be thinner than a coat of varnish.

 We also have a pretty cool moon.

It is tidally locked to our planet, so we only see one face; I suggest you pause this video from time to time:

This is the famous “pale blue dot” photograph:

That’s the Earth from about 6 billion kilometres away, taken by Voyager I over 20 years ago just before it left the solar system. Missed it? It’s the bluish pixel in the orangey band. Voyager I continues to operate and send astronomical data back to Earth. Carl Sagan said of this photograph:

“We succeeded in taking that picture [from deep space], and, if you look at it, you see a dot. That’s here. That’s home. That’s us. On it, everyone you ever heard of, every human being who ever lived, lived out their lives. The aggregate of all our joys and sufferings, thousands of confident religions, ideologies and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilizations, every king and peasant, every young couple in love, every hopeful child, every mother and father, every inventor and explorer, every teacher of morals, every corrupt politician, every superstar, every supreme leader, every saint and sinner in the history of our species, lived there on a mote of dust, suspended in a sunbeam.”

Well said, Carl.


Mars is pretty easy to get excited about. Rather than explain why, let’s hear it in song.

The Valles Marineris on the surface of Mars is the largest canyon in the solar system. It is over 4,000km wide.

It’s pretty deep too! This picture shows wind velocities on the surface:

If we turn away from the Valles Marineris,

…we see another “largest” that Mars boasts; largest mountain/volcano, Olympus Mons.

 At about 25km tall, it is more than three times the height of Everest. Here’s a shot of one of the poles; both poles of Mars are primarily CO2 ice (“dry ice”), but each has water ice in it as well.

Sunrise on Mars:

The Earth from Mars:

Mars has two moons, Phobos:

and Deimos:

They’re quite different in size, as this photograph shows:

This is the view of a Martian eclipse, courtesy of Phobos:

The surface is calm, but not still.

That’s because it has an atmosphere!

This was taken by the Mars Rover Opportunity of the Victoria Crater; you can see where the wind has had an effect in the centre:

If you’re really curious, check out Google Mars. This has been mapped by flyovers (as you can probably tell), so the map is not high quality everywhere.

Next time: The Asteroid Belt, Jupiter and Saturn!


~ by Andrew on August 23, 2011.

One Response to “SPACE pt. 1 – The Terrestrial Planets”


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