The moon may be a mostly uniform expanse of gray, but if you look closely, you can still find a few nooks and crannies in its surface, from deep trenches to pits and maybe even caves.

Now, researchers at CU Boulder have set out to explore what the environment might be like inside some of these shadowy features—many of which are too dark to see clearly from orbit.

The team's preliminary results suggest that pits and caves on the moon showcase remarkably stable conditions. They don't seem to experience the wild swings in temperature that are common at the moon's surface, said Andrew Wilcoski, a graduate student in the Department of Astrophysical and Planetary Sciences at CU Boulder. He will present the group's initial findings Friday at the American Geophysical Union fall meeting in New Orleans.

"If we're hoping to send people into these caves in the decades ahead, we want to know what they should expect down there," said Wilcoski, a co-author of the new research.

A Japanese space tourist on Monday rejected criticism from those who questioned his decision to pay a fortune for a trip to the International Space Station, saying the "amazing" experience was worth it.

It doesn't take a rocket scientist to know space is weird. But just how weird might surprise you. Space is dominated by invisible electromagnetic forces that we typically don't feel. It's also full of bizarre types of matter that we never experience on Earth. Here's five unearthly things that happen almost exclusively in outer space.

1. Plasma

On Earth, matter typically assumes one of three states: solid, liquid, or gas. But in space, 99.9% of normal matter is in an entirely different form—plasma. Made of loose ions and electrons, this substance is in a supercharged state beyond gas that's created when matter is heated to extreme temperatures or is plied with a strong electric current.

Although we rarely interact with plasma, we see it all the time. All the stars in the night sky, including the sun, are mostly made of plasma. It even appears occasionally on Earth in the form of bolts of lightning and in neon signs.

In comparison to gas, where individual particles chaotically zoom about, plasma can act collectively, like a team. It both conducts electricity and is influenced by electromagnetic fields—which operate under the very same force that keeps magnets on your fridge.

Through a new 3D real-time visualization tool, you can now explore the asteroids and comets that approach Earth's orbital neighborhood—and the spacecraft that visit these objects—with a click or a swipe. NASA's Eyes on Asteroids brings this data to any smartphone, tablet, or computer with an internet connection—no download required.

Thousands of asteroids and dozens of comets are discovered every single year, some of which—called near-Earth objects (NEOs)—follow orbits that pass through the inner solar system.