Seeing how it's the end of the school year again, it's seems the right time for another astro quiz, one with maybe just a bit if chemistry and geology thrown in for good measure. Don't worry, I know summer is on your mind, so this quiz will be just two true-or-false statements. Ready?

1. Uranus and Neptune have atmospheres rich in methane. One well-placed match would set them on fire!!!

Methane is a tiny molecule, the simplest of the hydrocarbons, CH4. Just one carbon surrounded nicely by four well-placed hydrogens, it is a powerful little energy storage unit.

Methane is in our atmosphere in very small amounts, measured in just parts per billion. Its sources are not exactly something to talk about over dinner. Rotting vegetation gives it off. Termites do. The world's millions of cattle and sheep… ahem… release tons and tons of the gas into the atmosphere every year. And - cover the children's ears - you and I donate our fair share, as well.

Methane is one of our planet's greenhouse gases, helping to keep our atmosphere nice and comfy. But it can burn, too. It is the gas that heats our ovens and stoves. One little match fires up that gas and *poof* we have ourselves a flame.

Uranus and Neptune both have a load of methane in their atmosphere. It is the reason both planets are bluish-green, believe it or not. Methane absorbs the red end of the sun's spectrum of light and reflects away the blue.

So why haven't both planets just lit up like fireballs? Because there is one ingredient missing: oxygen. Fuel needs oxygen to burn. The fuel alone, even with an available spark, would just sit there.

Thankfully for those Uranians and Neptunians there is no oxygen up there to fire up their giant planets.

2. The biggest known volcano in the solar system is on a little planet we call Mars.

How can that possibly be true? We have gigantic, nasty mountains of exploding rock right here: Etna, Vesuvius, Pinatubo. Our largest is the Big Island of Hawaii, over 30,000 feet high from head to toe. Mars? Mars is just a puny little rock half our size.

Well... Earth's inner make-up and its overall size don't really allow us to have supergigantic mountains and volcanoes. Our bigger size means a greater gravity, which keeps our mountains from poking too high into the sky. They just get pulled back down and spread out like cold Silly Putty.

And potential contenders for Solar System's Biggest Mountain, like the Big Island, don't have enough time to build up much higher. The plate the islands are riding on is moving over a hot spot in the middle of the Pacific Ocean.

A hot spot below a plate can cause a leak in that plate. By the time an island builds up substantially from magma oozing up through the leak, the plate it's riding on has already passed beyond the hot spot and a new island down the line is forming from a new leak.

Moreover, the island gets weathered eventually all the way down to the sea, which is why island chains like Hawaii can only stretch out so far before their islands go submarine. Mars, in comparison, has no oceans and essentially no atmosphere to tear down any great mountains.

Olympus Mons on Mars was a big leaky hole in the crust that just kept spewing magma from one stationary place. No plate tectonics moved it away from its hot spot.

And Mars' gravity is weak enough that the volcano could build higher and higher and higher. It stands now at about 89,000 feet and covers an area the size of our neighbor, Arizona.

That is one colossal mountain and winner of Biggest in the Solar system.

How did you do? Did you at least learn something new? Good, because that is what's really important here.

Until next time, clear skies!