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By NASA
5 Min Read What Are Asteroids? (Ages 14-18)
What are asteroids?
Asteroids are rocky objects that orbit the Sun just like planets do. In fact, sometimes asteroids are called “minor planets.” These space rocks were left behind after our solar system formed about 4.6 billion years ago.
Asteroids are found in a wide range of sizes. For example, one small asteroid, 2015 TC25, has a diameter of about 6 feet – about the size of a small car – while the asteroid Vesta is nearly 330 miles in diameter, almost as wide as the U.S. state of Arizona. Some asteroids even have enough gravity to have one or two small moons of their own.
There are more than a million known asteroids. Many asteroids are given names. An organization called the International Astronomical Union is responsible for assigning names to objects like asteroids and comets.
This illustration depicts NASA’s Psyche spacecraft as it approaches the asteroid Psyche. Once it arrives in 2029, the spacecraft will orbit the metal-rich asteroid for 26 months while it conducts its science investigation.NASA/JPL-Caltech/ASU What’s the difference between asteroids, meteors, and comets?
Although all of these celestial bodies orbit the Sun, they are not the same. Unlike asteroids, which are rocky, comets are a mix of dust and ice. Meteors are small space rocks that get pulled close enough to enter Earth’s atmosphere, where they either burn up as a shooting star or land on the ground as a meteorite.
What are asteroids made of?
Different types of asteroids are composed of different mixes of materials. Most of them are made of chondrites, which are combinations of materials such as rocks and clay. These are called “C-type” asteroids. Some, called “S-type,” are made of stony materials, while “M-type” asteroids are composed of metallic elements.
NASA’s Dawn spacecraft captured this image of Vesta as it left the giant asteroid’s orbit in 2012. The framing camera was looking down at the north pole, which is in the middle of the image.NASA/JPL-Caltech/UCLA/MPS/DLR/IDA How did the asteroids form?
Asteroids formed around the same time and in the same way as the planets in our solar system. A massive, dense cloud of gas and dust collapsed into a spinning disk, and the gravity in the disk’s center pulled more and more material toward it. Over time, these pieces repeatedly collided with each other, sometimes resulting in smaller fragments and other times clumping together, resulting in much bigger objects.
Objects with a lot of mass – like planets – produced enough gravity to pull themselves into spheres, but many smaller objects didn’t. These ended up becoming comets, small moons, and, yes, asteroids. Although some asteroids have a spherical shape, most have irregular shapes – sometimes oblong, bumpy, or jagged.
The main asteroid belt lies between Mars and Jupiter, and Trojan asteroids both lead and follow Jupiter. Scientists now know that asteroids were the original “building blocks” of the inner planets. Those that remain are airless rocks that failed to adhere to one another to become larger bodies as the solar system was forming 4.6 billion years ago.Credits: NASA, ESA and J. Olmsted (STScI) Where are asteroids found?
Most of the asteroids we know about are located in an area called the main asteroid belt, which is found in the space between Mars and Jupiter. But asteroids are found in other parts of the solar system, too.
Trojan asteroids orbit the Sun on the same orbital path as a planet. They’re found at two specific points on the planetary orbit called Lagrange points. At these points, the gravitational pull of the planet and the Sun are in balance, making these points gravity-neutral and stable. Many planets have been found to have Trojan asteroids, including Earth.
An asteroid’s location can also be influenced by the gravity of planets it passes and end up pushed or pulled onto a path that brings it close to Earth. When asteroids or comets are on an orbital path that comes within 30 million miles of Earth’s orbit, we call them near-Earth objects.
Illustration of NASA’s DART spacecraft and the Italian Space Agency’s (ASI) LICIACube, with images of the asteroids Dimorphos and Didymos obtained by the DART spacecraft.Credit: NASA/Johns Hopkins APL/Joshua Diaz Could an asteroid come close enough to hit Earth?
Yes! Throughout history, asteroids or pieces of asteroids have collided with Earth, our Moon, and the other planets, too. The effects of some of these impacts are still visible. For example, Chicxulub Crater was created 65 million years ago when a massive asteroid struck Mexico’s Yucatan Peninsula. The resulting cloud of dust and gas released into Earth’s atmosphere blocked sunlight, leading to a mass extinction that included the dinosaurs. More recently, in 2013, people in Chelyabinsk, Russia, witnessed an asteroid almost as wide as a tennis court explode in the atmosphere above them. That event produced a powerful shockwave that caused injuries and damaged structures.
This is why NASA’s Planetary Defense Coordination Office keeps a watchful eye on near-Earth objects. The Planetary Defense team relies on telescopes and observatories on Earth and in space to detect and monitor objects like these that could stray too close to our planet.
The agency is working on planetary defense strategies to use if an asteroid is discovered to be heading our way. For example, NASA’s DART (Double Asteroid Redirection Test) mission in 2022 was a first-of-its-kind test: an uncrewed spacecraft with an autonomous targeting system intentionally flew into the asteroid Dimorphos, successfully changing its orbit.
Jason Dworkin, OSIRIS-REx mission project scientist, holds up a vial containing part of the sample from asteroid Bennu in 2023.Credit: NASA/James Tralie How does NASA study asteroids?
NASA detects and tracks asteroids using telescopes on the ground and in space, radar observations, and computer modeling. The agency also has launched several robotic explorers to learn more about asteroids. Some missions study asteroids from above, such as the Psyche mission, launched in 2023 to study the asteroid Psyche beginning in 2029. Other missions have actually made physical contact with asteroids. For example, the DART mission mentioned above impacted an asteroid to change its orbit, and the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification and Security – Regolith Explorer) spacecraft collected a sample of material from the surface of asteroid Bennu and delivered the sample to Earth in 2023 for scientists to study.
Career Corner
Want a career where you get to study asteroids? Here are some jobs at NASA that do just that:
Astronomer: These scientists observe and study planets, stars, and galaxies. Astronomers make discoveries that help us understand how the universe works and how it is changing. This job requires a strong educational background in science, math, and computer science. Geologist: Asteroids are made of different types of rock, clay, or metallic materials. Geologists study the properties and composition of these materials to learn about the processes that have shaped Earth and other celestial bodies, like planets, moons, and asteroids. More About Asteroids
Asteroid Facts
Gallery: What’s That Space Rock?
Center for Near Earth Object Studies
Planetary Defense at NASA
Asteroid Watch: Keeping an Eye on Near-Earth Objects
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By NASA
5 min read
How NASA Science Data Defends Earth from Asteroids
Artist’s impression of NASA’s DART mission, which collided with the asteroid Dimorphos in 2022 to test planetary defense techniques. Open science data practices help researchers identify asteroids that pose a hazard to Earth, opening the possibility for deflection should an impact threat be identified. NASA/Johns Hopkins APL/Steve Gribben The asteroid 2024 YR4 made headlines in February with the news that it had a chance of hitting Earth on Dec. 22, 2032, as determined by an analysis from NASA’s Center for Near Earth Object Studies (CNEOS) at the agency’s Jet Propulsion Laboratory in Southern California. The probability of collision peaked at over 3% on Feb. 18 — the highest ever recorded for an object of its size. This sparked concerns about the damage the asteroid might do should it hit Earth.
New data collected in the following days lowered the probability to well under 1%, and 2024 YR4 is no longer considered a potential Earth impactor. However, the event underscored the importance of surveying asteroid populations to reveal possible threats to Earth. Sharing scientific data widely allows scientists to determine the risk posed by the near-Earth asteroid population and increases the chances of identifying future asteroid impact hazards in NASA science data.
“The planetary defense community realizes the value of making data products available to everyone,” said James “Gerbs” Bauer, the principal investigator for NASA’s Planetary Data System Small Bodies Node at the University of Maryland in College Park, Maryland.
How Scientists Spot Asteroids That Could Hit Earth
Professional scientists and citizen scientists worldwide play a role in tracking asteroids. The Minor Planet Center, which is housed at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, collects and verifies vast numbers of asteroid and comet position observations submitted from around the globe. NASA’s Small Bodies Node distributes the data from the Minor Planet Center for anyone who wants to access and use it.
A near-Earth object (NEO) is an asteroid or comet whose orbit brings it within 120 million miles of the Sun, which means it can circulate through Earth’s orbital neighborhood. If a newly discovered object looks like it might be an NEO, information about the object appears on the Minor Planet Center’s NEO Confirmation Page. Members of the planetary science community, whether or not they are professional scientists, are encouraged to follow up on these objects to discover where they’re heading.
The asteroid 2024 YR4 as viewed on January 27, 2025. The image was taken by the Magdalena Ridge 2.4m telescope, one of the largest telescopes in NASA’s Planetary Defense network. Asteroid position information from observations such as this one are shared through the Minor Planet Center and NASA’s Small Bodies Node to help scientists pinpoint the chances of asteroids colliding with Earth. NASA/Magdalena Ridge 2.4m telescope/New Mexico Institute of Technology/Ryan When an asteroid’s trajectory looks concerning, CNEOS alerts NASA’s Planetary Defense Coordination Office at NASA Headquarters in Washington, which manages NASA’s ongoing effort to protect Earth from dangerous asteroids. NASA’s Planetary Defense Coordination Office also coordinates the International Asteroid Warning Network (IAWN), which is the worldwide collaboration of asteroid observers and modelers.
Orbit analysis centers such as CNEOS perform finer calculations to nail down the probability of an asteroid colliding with Earth. The open nature of the data allows the community to collaborate and compare, ensuring the most accurate determinations possible.
How NASA Discovered Risks of Asteroid 2024 YR4
The asteroid 2024 YR4 was initially discovered by the NASA-funded ATLAS (Asteroid Terrestrial-impact Last Alert System) survey, which aims to discover potentially hazardous asteroids. Scientists studied additional data about the asteroid from different observatories funded by NASA and from other telescopes across the IAWN.
At first, 2024 YR4 had a broad uncertainty in its future trajectory that passed over Earth. As the planetary defense community collected more observations, the range of possibilities for the asteroid’s future position on Dec. 22, 2032 clustered over Earth, raising the apparent chances of collision. However, with the addition of even more data points, the cluster of possibilities eventually moved off Earth.
This visualization from NASA’s Center for Near Earth Object Studies shows the evolution of the risk corridor for asteroid 2024 YR4, using data from observations made up to Feb. 23, 2025. Each yellow dot represents the asteroid’s possible location on Dec. 22, 2032. As the range of possible locations narrowed, the dots at first converged on Earth, before skewing away harmlessly. NASA/JPL/CNEOS Having multiple streams of data available for analysis helps scientists quickly learn more about NEOs. This sometimes involves using data from observatories that are mainly used for astrophysics or heliophysics surveys, rather than for tracking asteroids.
“The planetary defense community both benefits from and is beneficial to the larger planetary and astronomy related ecosystem,” said Bauer, who is also a research professor in the Department of Astronomy at the University of Maryland. “Much of the NEO survey data can also be used for searching astrophysical transients like supernova events. Likewise, astrophysical sky surveys produce data of interest to the planetary defense community.”
How Does NASA Stop Asteroids From Hitting Earth?
In 2022, NASA’s DART (Double Asteroid Redirection Test) mission successfully impacted with the asteroid Dimorphos, shortening the time it takes to orbit around its companion asteroid Didymos by 33 minutes. Didymos had no chance of hitting Earth, but the DART mission’s success means that NASA has a tested technique to consider when addressing a future asteroid potential impact threat.
Artist’s impression of NASA’s upcoming NEO Surveyor mission, which will search for potentially hazardous near-Earth objects. The mission will follow open data practices to improve the chances of identifying dangerous asteroids. NASA/JPL-Caltech To increase the chances of discovering asteroid threats to Earth well in advance, NASA is working on a new space-based observatory, NEO Surveyor, which will be the first spacecraft specifically designed to look for asteroids and comets that pose a hazard to Earth. The mission is expected to launch in the fall of 2027, and the data it collects will be available to everyone through NASA archives.
“Many of the NEOs that pose a risk to Earth remain to be found,” Bauer said. “An asteroid impact has a very low likelihood at any given time, but consequences could be high, and open science is an important component to being vigilant.”
For more information about NASA’s approach to sharing science data, visit:
https://science.nasa.gov/open-science.
By Lauren Leese
Web Content Strategist for the Office of the Chief Science Data Officer
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Last Updated Apr 10, 2025 Related Terms
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By NASA
Jonathan Gardner of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, was selected as a 2023 Fellow of the American Astronomical Society (AAS) for extraordinary achievement and service. He is being recognized for exceptional community service and scientific leadership of NASA’s James Webb Space Telescope science teams, leading to Webb’s flight hardware exceeding all of its requirements.
Dr. Jonathan Gardner is the Deputy Senior Project Scientist for the James Webb Space Telescope at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.Credits: Courtesy of Jonathan Gardner Gardner is the deputy senior project scientist for the Webb telescope in Goddard’s Astrophysics Science Division. Webb, which launched Dec. 25, 2021, is the largest, most powerful, and most complex space science telescope ever built. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.
John Mather, senior project scientist on Webb and a senior astrophysicist at Goddard, nominated Gardner for the fellowship. In his nomination, Mather wrote:
“Jonathan Gardner is a quiet superstar, well known to the Webb community. As deputy senior project scientist for Webb, Gardner represents the senior project scientist in all aspects of the mission, with responsibility for ensuring Webb’s scientific performance. Gardner is a tireless advocate for the scientific vision and its accurate implementation. He is the main spokesperson for Webb science throughout NASA and in the wider astronomy community. He is the person most responsible for keeping the science teams working well together and for communicating with other astronomers.”
Gardner began working on Webb as a member of the Ad-Hoc Science Working Group in the late 1990s, joining the project as the deputy senior project scientist in 2002.
Beginning in 2002, Gardner organized all the meetings and communications of the Science Working Group, which included people from the U.S., Europe, and Canada, including instrument teams and other partners. He recruited Goddard scientists for the mission’s Project Science Team, and ensured a scientist was assigned to every engineering topic. Gardner also wrote and published the scientific requirements in a dedicated issue of Space Science Reviews. He set up the Science Requirements Analysis Board to review any potential threats to the scientific goals of the mission and worked with engineering teams to avoid any failures. He represented scientific interests throughout the engineering project and throughout NASA, by ensuring regular communication between scientists, managers, and engineers.
The 2023 AAS Fellows are recognized for enhancing and sharing humanity’s scientific understanding of the universe through personal achievement and extraordinary service to the astronomical sciences and to the AAS.
AAS, established in 1899, is a major international organization of professional astronomers, astronomy educators, and amateur astronomers. Its membership of approximately 8,000 also includes physicists, geologists, engineers, and others whose interests lie within the broad spectrum of subjects now comprising the astronomical sciences. The mission of the AAS is to enhance and share humanity’s scientific understanding of the universe as a diverse and inclusive astronomical community, which it achieves through publishing, meetings, science advocacy, education and outreach, and training and professional development.
For information about NASA and agency programs, visit: https://www.nasa.gov
By Robert Gutro
NASA’s Goddard Space Flight Center, Greenbelt, Md.
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By NASA
In 2023, NASA Langley’s workforce brought imagination to reality with innovative technological development and a continued commitment to tackling some of the tough challenges that both NASA and the nation face.
NASA At NASA, we aspire to know more, dig deeper, climb higher and along the way we are asking, ‘What if?’,” said NASA Langley Center Director Clayton P. Turner in an introductory message to Langley’s 2023 Annual Report. “Our inquisitive nature propels us on our mission to reach for new heights and reveal the unknown for the benefit of humankind.”
All year, the Langley workforce pondered and planned for a future alongside self-flying drones, aircraft with reduced emissions, air travel that benefits from greater fuel efficiency and space exploration assisted by inflatable heat shields that could give us the ability to carry greater payloads than ever before.
“We invite you to explore all that NASA’s Langley Research Center has to offer — our amazing people, unique capabilities, and legacy of success,” Turner said in his introduction.
Use this link to explore the 2023 Annual Report for NASA’s Langley Research Center.
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By NASA
3 min read
2023 Entrepreneurs Challenge Winner Skyline Nav AI: Revolutionizing GPS-Independent Navigation with Computer Vision
NASA sponsored Entrepreneurs Challenge events in 2020, 2021, and 2023 to identify innovative ideas and technologies from small business start-ups with the potential to advance the agency’s science goals. To help leverage external funding sources for the development of innovative technologies of interest to NASA, SMD involved the venture capital community in Entrepreneurs Challenge events. Challenge winners were awarded prize money, and in 2023 the total Entrepreneurs Challenge prize value was $1M. Numerous challenge winners have subsequently received funding from both NASA and external sources (e.g., other government agencies or the venture capital community) to further develop their technologies.
Skyline Nav AI, a winner of the 2023 NASA Entrepreneurs Challenge, is pioneering GPS-independent navigation by leveraging cutting-edge computer vision models, artificial intelligence (AI), and edge computing.
Skyline Nav AI’s flagship technology offers precise, real-time geolocation without the need for GPS, Wi-Fi, or cellular networks. The system utilizes machine learning algorithms to analyze terrain and skyline features and match them with preloaded reference datasets, providing up to centimeter-level accuracy in GPS-denied environments. This capability could enable operations in areas where GPS signals are absent, blocked, degraded, spoofed, or jammed, including urban canyons, mountainous regions, and the Moon.
Skyline Nav AI’s flagship technology at work in New York to provide precise location by matching the detected skyline with a reference data set. The red line shows detection by Skyline Nav AI technology, the green line marks the true location in the reference satellite dataset, and the orange line represents the matched location (i.e., the location extracted from the satellite dataset using Skyline Nav AI algorithms). Skyline Nav’s visual navigation technology can deliver accuracy up to five meters, 95% of the time. The AI-powered visual positioning models continuously improve geolocation precision through pixel-level analysis and semantic segmentation of real-time images, offering high reliability without the need for GPS.
In addition to its visual-based AI, Skyline Nav AI’s software is optimized for edge computing, ensuring that all processing occurs locally on the user’s device. This design enables low-latency, real-time decision-making without constant satellite or cloud-based connectivity, making it ideal for disconnected environments such as combat zones or space missions.
Furthermore, Skyline Nav AI’s technology can be integrated with various sensors, including inertial measurement units (IMUs), lidar, and radar, to further enhance positioning accuracy. The combination of visual navigation and sensor fusion can enable centimeter-level accuracy, making the technology potentially useful for autonomous vehicles, drones, and robotics operating in environments where GPS is unreliable.
“Skyline Nav AI aims to provide the world with an accurate, resilient alternative to GPS,” says Kanwar Singh, CEO of Skyline Nav AI. “Our technology empowers users to navigate confidently in even the most challenging environments, and our recent recognition by NASA and other partners demonstrates the value of our innovative approach to autonomous navigation.”
Skyline Nav AI continues to expand its influence through partnerships with organizations such as NASA, the U.S. Department of Defense, and the commercial market. Recent collaborations include projects with MIT, Draper Labs, and AFRL (Air Force Research Laboratory), as well as winning the MOVE America 2024 Pitch competition and being a finalist in SXSW 2024.
Sponsoring Organization: The NASA Science Mission Directorate sponsored the Entrepreneurs Challenge events.
Project Leads: Kanwar Singh, Founder & CEO of Skyline Nav AI
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Last Updated Jan 07, 2025 Related Terms
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