Asteroidbelt - Blog Posts

Here’s What You Need to Know About Near-Earth Objects

Our solar system is littered with asteroids and comets, and sometimes they get a little close to Earth. But no need to worry! This happens all the time. When an asteroid or comet could come close to our planet, it’s known as a near-Earth object – aka NEO.

But how close is “close”?

A near-Earth object is defined as an object that could pass by our Earth within 30 million miles. We begin to keep close watch on objects that could pass within 5 million miles of our planet.

To put that into perspective, our Moon is only 238,900 miles away.

However unlikely an impact is, we want to know about all near-Earth objects. Our Planetary Defense Coordination Office maintains watch for asteroids and comets coming close to Earth. Along with our partners, we discover, catalog and characterize these bodies.

But what if one of these objects posed a threat?

We want to be prepared. That is why we are working on several deflection techniques and technologies to help protect our planet.

So next time that you hear of an asteroid passing “close” to Earth, know that it’s just one of many that we are tracking.

Here are 10 more things you should know about Planetary Defense.

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Solar System: Things to Know This Week

Our Dawn mission to the asteroid belt is no ordinary deep space expedition. 

Instead of traditional chemical rockets, the spacecraft uses sophisticated ion engines for propulsion. This enabled Dawn to become the first mission to orbit not one, but two different worlds — first the giant asteroid Vesta and now the dwarf planet Ceres. Vesta and Ceres formed early in the solar system's history, and by studying them, the mission is helping scientists go back in time to the dawn of the planets. To mark a decade since Dawn was launched on Sept. 27, 2007, here are 10 things to know about this trailblazing mission.

1. Ion Engines: Not Just for Sci-Fi Anymore

Most rocket engines use chemical reactions for propulsion, which tend to be powerful but short-lived. Dawn's futuristic, hyper-efficient ion propulsion system works by using electricity to accelerate ions (charged particles) from xenon fuel to a speed seven to 10 times that of chemical engines. Ion engines accelerate the spacecraft slowly, but they're very thrifty with fuel, using just milligrams of xenon per second (about 10 ounces over 24 hours) at maximum thrust. Without its ion engines, Dawn could not have carried enough fuel to go into orbit around two different solar system bodies. Try your hand at an interactive ion engine simulation.

2. Time Capsules 

Scientists have long wanted to study Vesta and Ceres up close. Vesta is a large, complex and intriguing asteroid. Ceres is the largest object in the entire asteroid belt, and was once considered a planet in its own right after it was discovered in 1801. Vesta and Ceres have significant differences, but both are thought to have formed very early in the history of the solar system, harboring clues about how planets are constructed. Learn more about Ceres and Vesta—including why we have pieces of Vesta here on Earth.

3. Portrait of a Dwarf Planet

This view of Ceres built from Dawn photos is centered on Occator Crater, home of the famous "bright spots." The image resolution is about 460 feet (140 meters) per pixel.

Take a closer look.

4. What's in a Name? 

Craters on Ceres are named for agricultural deities from all over the world, and other features carry the names of agricultural festivals. Ceres itself was named after the Roman goddess of corn and harvests (that's also where the word "cereal" comes from). The International Astronomical Union recently approved 25 new Ceres feature names tied to the theme of agricultural deities. Jumi, for example, is the Latvian god of fertility of the field. Study the full-size map.

5. Landslides or Ice Slides? 

Thanks to Dawn, evidence is mounting that Ceres hides a significant amount of water ice. A recent study adds to this picture, showing how ice may have shaped the variety of landslides seen on Ceres today.

6. The Lonely Mountain 

Ahuna Mons, a 3-mile-high (5-kilometer-high) mountain, puzzled Ceres explorers when they first found it. It rises all alone above the surrounding plains. Now scientists think it is likely a cryovolcano — one that erupts a liquid made of volatiles such as water, instead of rock. "This is the only known example of a cryovolcano that potentially formed from a salty mud mix, and that formed in the geologically recent past," one researcher said. Learn more.

7. Shining a Light on the Bright Spots 

The brightest area on Ceres, located in the mysterious Occator Crater, has the highest concentration of carbonate minerals ever seen outside Earth, according to studies from Dawn scientists. Occator is 57 miles (92 kilometers) wide, with a central pit about 6 miles (10 kilometers) wide. The dominant mineral of this bright area is sodium carbonate, a kind of salt found on Earth in hydrothermal environments. This material appears to have come from inside Ceres, and this upwelling suggests that temperatures inside Ceres are warmer than previously believed. Even more intriguingly, the results suggest that liquid water may have existed beneath the surface of Ceres in recent geological time. The salts could be remnants of an ocean, or localized bodies of water, that reached the surface and then froze millions of years ago. See more details.

8. Captain's Log 

Dawn's chief engineer and mission director, Marc Rayman, provides regular dispatches about Dawn's work in the asteroid belt. Catch the latest updates here.

9. Eyes on Dawn 

Another cool way to retrace Dawn's decade-long flight is to download NASA's free Eyes on the Solar System app, which uses real data to let you go to any point in the solar system, or ride along with any spacecraft, at any point in time—all in 3-D.

10. No Stamp Required

Send a postcard from one of these three sets of images that tell the story of dwarf planet Ceres, protoplanet Vesta, and the Dawn mission overall.

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It’s International Asteroid Day!

There are more than 700,000 known asteroids, but how much do you know about these rocky remnants left over from the birth of our solar system 4.6 billion years ago? 

Today, June 30 is International Asteroid Day. Here are some things to know about our fascinating space rubble.

1. A Place in Space 

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.

3. Small Overall 

If all of the asteroids were combined into a ball, they would still be much smaller than the Earth's moon.

4. Except for a Big One

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.

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Two New Missions to Explore the Early Solar System

We’ve got big science news…!

We’ve just added two more science missions to our lineup! The two selected missions have the potential to open new windows on one of the earliest eras in the history of our solar system – a time less than 10 millions years after the birth of our sun.

The missions, known as Lucy and Psyche, were chosen from five finalists and will proceed to mission formulation.

Let’s take a dive into each mission…

Lucy

Lucy, a robotic spacecraft, will visit a target-rich environment of Jupiter’s mysterious Trojan asteroids. Scheduled to launch in October 2021, the spacecraft is slated to arrive at its first destination, a main asteroid belt, in 2025. 

Then, from 2027 to 2033, Lucy will explore six Jupiter Trojan asteroids. These asteroids are trapped by Jupiter’s gravity in two swarms that share the planet’s orbit, one leading and one trailing Jupiter in its 12-year circuit around the sun. The Trojans are thought to be relics of a much earlier era in the history of the solar system, and may have formed far beyond Jupiter’s current orbit.

Studying these Trojan asteroids will give us valuable clues to deciphering the history of the early solar system.

Psyche

The Psyche mission will explore one of the most intriguing targets in the main asteroid belt – a giant metal asteroid, known as 16 Psyche, about three times farther away from the sun than is the Earth. The asteroid measures about 130 miles in diameter and, unlike most other asteroids that are rocky or icy bodies, it is thought to be comprised of mostly metallic iron and nickel, similar to Earth’s core.

Scientists wonder whether psyche could be an exposed core of an early planet that could have been as large as Mars, but which lost its rocky outer layers due to a number of violent collisions billions of years ago.

The mission will help scientists understand how planets and other bodies separated into their layers early in their histories. The Psyche robotic mission is targeted to launch in October of 2023, arriving at the asteroid in 2030, following an Earth gravity assist spacecraft maneuver in 2024 and a Mars flyby in 2025.

Get even more information about these two new science missions HERE. 

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