Izzy, do you want to guess at the melting point of rock?

I-O has hundreds of volcanoes erupting, and it's a smaller world. It's not much bigger than our own moon.

Venus is even hotter than Mercury. So can we call it a fiery world?

Hello, welcome to the supermassive podcast from the Royal Astronomical Society, with, science journalist Izzy Clark and astrophysicist

Dr Becky Smethurst. Yeah, this month we're doing what the British summer here has not done

and we're turning up the heat, right? We're exploring the fiery worlds in our solar system from planets

close to the sun to distant worlds of fire and lava.

And to help us, we'll be joined by planetary scientist Professor David Rothery from the Open

University and we'll hear from Professor Alfred McEwen who wants to send a mission to Jupiter's

Moon I.O. And you know the drill by now, Dr. Robert Massey, the deputy

director of the Royal Astronomical Society, is here too. So let's get this straight, Robert.

What classifies something, whether that is a planet or an object, as fiery?

Well, I think we think about this. There are a lot of fiery worlds out there. And even

before the space age, you know, we would have been aware of the fact that Mercury, the closest

planet to the sun, was scorched by virtue of being closer to the sun. So during the day,

the temperature goes up to 427 degrees Celsius and at night down to minus 180, so you're simultaneously having a fiery

in an icy world. But if you go out to Venus, the next planet further out, and the closest

one to the Earth, we often think Mars has been the closest, but it's actually Venus. It's the same

size of the Earth, but it has a stupendously thick atmosphere with really high atmospheric pressure

at the surface. A big blanket of carbon dioxide.

So the surface temperature is even higher than on Mercury, 470 degrees Celsius, hot enough to melt lead.

And we think it might even have active volcanoes too. I definitely think that counts as a fiery world.

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