Asteroids—named by British astronomer William Herschel from the Greek expression meaning “star-like"—are rocky, airless worlds that are too small to be called planets. But what they might lack in size they certainly make up for in number: An estimated 1.1 to 1.9 million asteroids larger than 1 kilometer are in the Main Belt between the orbits of Mars and Jupiter. And there are millions more that are smaller in size. Asteroids range in size from Vesta—the largest at about 329 miles (529 kilometers) wide—to bodies that are just a few feet across.
2. What Lies Beneath
Asteroids are generally categorized into three types: carbon-rich, silicate, or metallic, or some combination of the three. Why the different types? It all comes down to how far from the sun they formed. Some experienced high temperatures and partly melted, with iron sinking to the center and volcanic lava forced to the surface. The asteroid Vesta is one example we know of today.
In 1801, Giuseppe Piazzi discovered the first and then-largest asteroid, Ceres, orbiting between Mars and Jupiter. Ceres is so large that it encompasses about one-fourth of the estimated total mass of all the asteroids in the asteroid belt. In 2006, its classification changed from asteroid to as a dwarf planet.
5. Mission to a Metal World
NASA’s Psyche mission will launch in 2022 to explore an all-metal asteroid—what could be the core of an early planet—for the very first time. And in October 2021, the Lucy mission will be the first to visit Jupiter’s swarms of Trojan asteroids.
6. Near-Earth Asteroids
The term ‘near’ in near-Earth asteroid is actually a misnomer; most of these bodies do not come close to Earth at all. By definition, a near-Earth asteroid is an asteroid that comes within 28 million miles (44 million km) of Earth’s orbit. As of June 19, 2017, there are 16,209 known near-Earth asteroids, with 1,803 classified as potentially hazardous asteroids (those that could someday pose a threat to Earth).
7. Comin’ in Hot
About once a year, a car-sized asteroid hits Earth’s atmosphere, creates an impressive fireball, and burns up before reaching the surface.
8. But We’re Keeping an Eye Out
Ground-based observatories and facilities such as Pan-STARRS, the Catalina Sky Survey, and ATLAS are constantly on the hunt to detect near-Earth asteroids. NASA also has a small infrared observatory in orbit about the Earth: NEOWISE. In addition to detecting asteroids and comets, NEOWISE also characterizes these small bodies.
9. Buddy System
Roughly one-sixth of the asteroid population have a small companion moon (some even have two moons). The first discovery of an asteroid-moon system was of asteroid Ida and its moon Dactyl in 1993.
10. Earthly Visitors
Several NASA space missions have flown to and observed asteroids. The NEAR Shoemaker mission landed on asteroid Eros in 2001 and NASA’s Dawn mission was the first mission to orbit an asteroid in 2011. In 2005, the Japanese spacecraft Hayabusa landed on asteroid Itokawa. Currently, NASA’s OSIRIS-REx is en route to a near-Earth asteroid called Bennu; it will bring a small sample back to Earth for study.
Our Psyche mission to a metal world, which will explore a giant metal asteroid known as 16 Psyche, is getting a new, earlier launch date. Psyche is now expected to launch from the Kennedy Space Center in 2022, cruise through the solar system for 4.6 years, and arrive at the Psyche asteroid in 2026, four years earlier than planned.
Below are 10 things to know about this mission to a completely new and unexplored type of world.
1. Psyche, Squared
Psyche is the name of the NASA space mission and the name of the unique metal asteroid orbiting the sun between Mars and Jupiter. The asteroid was discovered in 1852 by Italian astronomer Annibale de Gasparis and named after the Greek mythological figure Psyche, whom Cupid fell in love with. “Psyche” in Greek also means “soul.”
2. Mission: Accepted
The Psyche Mission was selected for flight earlier this year under NASA’s Discovery Program. And it will take a village to pull off: The spacecraft is being built by Space Systems Loral in Palo Alto, California; the mission is led by Arizona State University; and NASA’s Jet Propulsion Laboratory will be responsible for mission management, operations and navigation.
3. An Unusual Asteroid
For the very first time, this mission will let us examine a world made not of rock and ice, but metal. Scientists think Psyche is comprised mostly of metallic iron and nickel, similar to Earth’s core - which means Psyche could be an exposed core of an early planet as large as Mars.
4. Sweet 16
Psyche the asteroid is officially known as 16 Psyche, since it was the 16th asteroid to be discovered. It lies within the asteroid belt, is irregularly shaped, about the size of Massachusetts, and is about three times farther away from the sun than Earth.
5. Discoveries Abound
The Psyche mission will observe the asteroid for 20 months. Scientists hope to discover whether Psyche is the core of an early planet, how old it is, whether it formed in similar ways to Earth’s core, and what its surface is like. The mission will also help scientists understand how planets and other bodies separated into their layers including cores, mantles and crusts early in their histories. “Psyche is the only known object of its kind in the solar system and this is the only way humans will ever visit a core,” said Principal Investigator Lindy Elkins-Tanton of Arizona State University.
6. Think Fast
The mission launch and arrival were moved up because Psyche’s mission design team were able to plot a more efficient trajectory that no longer calls for an Earth gravity assist, ultimately shortening the cruise time. The new trajectory also stays farther from the sun, reducing the amount of heat protection needed for the spacecraft, and will still include a Mars flyby in 2023.
7. Gadgets Galore
The Psyche spacecraft will be decked out with a multispectral imager, gamma ray and neutron spectrometer, magnetometer, and X-band gravity science investigation. More: https://sese.asu.edu/research/psyche
8. Stunning Solar Panels
In order to support the new mission trajectory, the solar array system was redesigned from a four-panel array in a straight row on either side of the spacecraft to a more powerful five-panel x-shaped design, commonly used for missions requiring more capability. Much like a sports car, combining a relatively small spacecraft body with a very high-power solar array design means the Psyche spacecraft will be able to speed to its destination much faster. Check out this artist’s-concept illustration here: https://www.nasa.gov/image-feature/artists-concept-of-psyche-spacecraft-with-five-panel-array
9. See For Yourself
Watch the planned Psyche mission in action.
10. Even More Asteroids
Our missions to asteroids began with the orbiter NEAR of asteroid Eros, which arrived in 2000, and continues with Dawn, which orbited Vesta and is now in an extended mission at Ceres. The mission OSIRIS-REx, which launched on Sept. 8, 2016, is speeding toward a 2018 rendezvous with the asteroid Bennu, and will deliver a sample back to Earth in 2023. The Lucy mission is scheduled to launch in October 2021 and will explore six Jupiter Trojan asteroids. More: https://www.jpl.nasa.gov/news/news.php?feature=6713
Want to learn more? Read our full list of the 10 things to know this week about the solar system HERE.
The story begins with a person who is an orphan; or someone who feels like an orphan, alone, separate, different, and misunderstood. This character has questions about their circumstance (for example:”Why did my parents die?”, “Why doesn’t anyone like me?”, Why am I always in trouble?”, “What will I do with my life?”, etc.). These questions set off the journey.