Supernovas, black holes, exoplanets. We're fascinated with them, and who can blame us? But sometimes we forget to talk about the littler things out there like asteroids and moons which are critical to our understanding of the universe. The fact is, exploring small stuff might be the key to some of our greatest missions in space, like discovering the origins of the solar system, finding habitability and locating resources for future space travel. So this week, I bring you news from three missions dedicated to studying the little guys of space. I'm Caitlin Hofmeister and welcome to SciShow Space News.

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Last week, NASA officially began construction on its first spacecraft designed to sample an asteroid. The mission, called OSIRIS-REx, will travel to a 500 meter-wide asteroid in near-Earth orbit and steal a quick scoop of it to bring back to Earth. Its target will be the asteroid Bennu, a 4.5 billion year old time capsule dating back to the creation of the solar system. NASA's hoping that Bennu's chemistry will answer a lot of questions like whether water and organic molecules, the building blocks of life, were present at the time of the solar system's formation. Plus, finding water on Bennu would be incredibly handy as we begin to look to asteroids as possible way stations for future space missions, and we might find a wealth of materials like iron, nickel or titanium to boot. OSIRIS-REx will launch in September of 2016 and it'll enter orbit around Bennu two years later. Then it'll begin scanning its surface with three spectrometers to determine its chemical composition. Bennu's gravity is much lower than that of Earth's, so the craft won't be able to land. So by 2019 it'll choose the perfect point to snatch up some asteroid dust using a delightfully named instrument called a Touch-And-Go Sample Acquisition Mechanism, or TAGSAM. Then the little craft will hightail it back to Earth, releasing its sample return capsule which should arrive in 2023.

Now looking at space news much farther from home, astronomers in New Zealand and Tasmania said last week that they've observed what they think is the first known exomoon, that is, a moon orbiting an exoplanet. Details, however, are kind of sketchy, like so sketchy that the astronomers say they might be wrong. They think they could've seen either an exoplanet with a moon or a small, dim star being orbited by a planet. But either way, their observation was a big step toward finding exomoons in the future. Exomoons are really hard to find because they're so small and faint. Even small exoplanets can be nearly impossible to spot because they get lost in the glare of their stars. But a method called gravitational lensing combined with good planning may allow us to observe distant moons in the future. With gravitational lensing, a massive body in space can act as a really good lens for light that passes through its atmosphere from behind. That's how this mysterious body was spotted in the first place. The larger body magnified light from a distant star, and in that light the astronomers saw a smaller body. But the bigger body could've either been a planet or a very dim star of its own that's actually farther away than they thought. If only we knew how far away it was we'd be able to tell for sure. So like good scientists, the astronomers are gearing up to try it again. Using two distant telescopes fixed on the same point and observing the same lensing effect, they plan to triangulate the distance to the body and figure out how big it is. It's a simple solution called parallax that's served us well for more than a century, and it just maybe the key to discovering exomoons with confidence in the future.

And finally, another moon mission is drawing to an end. Last week, NASA said it expects the spacecraft known as LADEE to crash into the surface of the moon this Monday, April 21st. Since November, LADEE, also known as the Lunar Atmosphere and Dust Environment Explorer, has been collecting photos and measurements of the lunar atmosphere and now is ready to call it a day, or rather 140 or so days. At 100 trillionth of the density of the Earth's, the lunar atmosphere is probably like that of many other moons, small planets, and asteroids. So LADEE has been observing away sending loads of data back to Earth for analysis. Most notably, it seems to have solved the mystery of the strange streaky glow at sunrise that Apollo astronauts reported seeing in the 1970s. According to LADEE's observations, it was caused by airborne lunar dust that we weren't even sure was there. Good boy LADEE, thank you for a good six months.

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