This is planetary radio. Welcome back to your space show of shows. I'm Matt Kaplan. First there were cosmonauts. Soon after came astronauts. Now 42 years later

make room for the taikonauts. China has succeeded in becoming the third

nation to put a human in space.

We'll talk about this achievement with international space expert James Oberg,

and we'll hear from a JPL scientist with personal reasons to be proud of two space programs.

Bruce Betts is up to the usual monkey business in What's Up and will begin as usual with

Emily.

She's taking note of the changing seasons, but not just here on Earth. I'll be right

back. Hi, I'm Emily Lochawala with questions and answers. A listener asked, is the Earth the only

planet that has seasons?

Earth's seasons are caused because its rotational axis is tilted.

As a result of the Earth's tilt,

sometimes the South Pole is bathed in sunlight

24 hours a day, while the North Pole experiences darkness and sometimes

it's the other way around.

Summer and winter result from this changing amount of sunlight that the middle and high

latitudes of Earth receive over the course of a year.

The Earth is not the only planet in the solar system that has an axial tilt.

Mars's axial tilt is nearly the same as Earth's,

so Mars has seasonal variations in sunlight much like Earth's.

However, Mars's seasons are much more extreme than Earth's for two main reasons.

First, Mars's orbit around the Sun is much more elliptical than Earth's,

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