Asteroid 2001 FO32 Will Safely Pass by Earth March 21


Mar 11, 2021

Opening at the top of the observatory

This photo shows the view from inside the dome of NASA’s Infrared Telescope Facility during a night of observing. The 3.2-meter (10.5-foot) telescope atop Hawaii’s Mauna Kea will be used to measure the infrared spectrum of asteroid 2001 FO32.Credits: UH/IfA

The interplanetary interloper won’t come closer than 1.25 million miles to Earth, but it will present a valuable scientific opportunity for astronomers.

The largest asteroid predicted to pass by our planet in 2021 will be at its closest on March 21, providing astronomers a rare opportunity to get a good look at a rocky relic that formed at the dawn of our solar system.

Called 2001 FO32, the near-Earth asteroid will make its closest approach at a distance of about 1.25 million miles (2 million kilometers) – or 5 1/4 times the distance from Earth to the Moon. There is no threat of a collision with our planet now or for centuries to come.

“We know the orbital path of 2001 FO32 around the Sun very accurately, since it was discovered 20 years ago and has been tracked ever since,” said Paul Chodas, director of the Center for Near Earth Object Studies (CNEOS), which is managed by NASA’s Jet Propulsion Laboratory in Southern California. “There is no chance the asteroid will get any closer to Earth than 1.25 million miles.”

Still, that distance is close in astronomical terms, which is why 2001 FO32 has been designated a “potentially hazardous asteroid.” CNEOS computes high-precision orbits for near-Earth objects (NEOs) in support of NASA’s Planetary Defense Coordination Office, relying on telescopes and ground-based radar to help precisely characterize every NEO’s orbit to improve long-term hazard assessments.

During this approach, 2001 FO32 will pass by at about 77,000 mph (124,000 kph) – faster than the speed at which most asteroids encounter Earth. The reason for the asteroid’s unusually speedy close approach is its highly inclined and elongated (or eccentric) orbit around the Sun, an orbit that is tilted 39 degrees to Earth’s orbital plane. This orbit takes the asteroid closer to the Sun than Mercury and twice as far from the Sun as Mars.

As 2001 FO32 makes its inner solar system journey, the asteroid picks up speed like a skateboarder rolling down a halfpipe, and then slows after being flung back out into deep space and swinging back toward the Sun. It completes one orbit every 810 days (about 2 1/4 years).

Orbital diagram

This diagram depicts the elongated and inclined orbit of 2001 FO32 as it travels around the Sun (white ellipse). Because of this orbit, when the asteroid makes its close approach to Earth, it will be traveling at an unusually fast speed of 77,000 mph (124,000 kph).Credits: NASA/JPL-Caltech

After its brief visit, 2001 FO32 will continue its lonely voyage, not coming this close to Earth again until 2052, when it will pass by at about seven lunar distances, or 1.75 million miles (2.8 million kilometers).

Astronomical Geology

>Asteroid 2001 FO32 was discovered in March 2001 by the Lincoln Near-Earth Asteroid Research (LINEAR) program in Socorro, New Mexico, and had been estimated, based on optical measurements, to be roughly 3,000 feet (1 kilometer) wide. In more recent follow-up observations by NEOWISE, 2001 FO32 appears to be faint when observed in infrared wavelengths, which suggests the object is likely less than 1 kilometer in diameter. Analysis by the NEOWISE team shows that it is between 1,300 to 2,230 feet (440 to 680 meters) wide.

Even if it is at the smaller end of the scale, 2001 FO32 will still be the largest asteroid to pass this close to our planet in 2021. The last notably large asteroid close approach was that of 1998 OR2 on April 29, 2020. While 2001 FO32 is somewhat smaller than 1998 OR2, it will be three times nearer to Earth.

The March 21 encounter will provide an opportunity for astronomers to get a more precise understanding of the asteroid’s size and albedo (i.e. how bright, or reflective, its surface is), and a rough idea of its composition.

This will be achieved, in part, with the use of NASA’s Infrared Telescope Facility (IRTF), a 3.2-meter (10.5-foot) telescope atop Hawaii’s Mauna Kea that will observe the asteroid in the days leading up to close approach using its workhorse infrared spectrograph, SpeX. “We’re trying to do geology with a telescope,” said Vishnu Reddy, associate professor at the University of Arizona’s Lunar and Planetary Laboratory in Tucson.

When sunlight hits an asteroid’s surface, minerals in the rock absorb some wavelengths while reflecting others. By studying the spectrum of light reflecting off the surface, astronomers can measure the chemical “fingerprints” of the minerals on the surface of the asteroid. “We’re going to use the IRTF to get the infrared spectrum to see its chemical makeup,” Reddy explained. “Once we know that, we can make comparisons with meteorites on Earth to find out what minerals 2001 FO32 contains.”

For example, should 2001 FO32 be identified as iron-rich, that would mean it’s denser and therefore more massive than a stony asteroid of a similar size; observations showing a surface with low albedo (meaning that it’s dark) may indicate the asteroid contains a lot of carbon, suggesting it could be the nucleus of a long-dead comet.

A Closer Look

In addition, radar observations by the Deep Space Network (DSN) may be carried out to get a detailed view of the asteroid. An operation of NASA’s Space Communications and Navigation program (SCaN), the DSN comprises three ground stations – one in California (Goldstone), one in Spain (Madrid), and one in Australia (Canberra). Their dish antennas can be used to bounce radio signals off 2001 FO32 so that other radio antennas can receive them. Such radar observations can offer additional insight into the asteroid’s orbit, provide a better estimate of its dimensions and rotation rate, and help glimpse surface features (like large boulders or craters). They could even reveal any small satellites that may be in tow.

“Observations dating back 20 years revealed that about 15% of near-Earth asteroids comparable in size to 2001 FO32 have a small moon,” said Lance Benner, principal scientist at JPL. “Currently little is known about this object, so the very close encounter provides an outstanding opportunity to learn a great deal about this asteroid.”

Over 95% of near-Earth asteroids the size of 2001 FO32 or larger have been discovered, tracked, and cataloged. None of the large asteroids in the catalog has any chance of impacting Earth over the next century, and it is extremely unlikely that any of the remaining undiscovered asteroids of this size could impact Earth, either. Still, efforts continue to discover all asteroids that could pose an impact hazard. The more information that can be gathered about these objects, the better mission designers can prepare to deflect them if any were to threaten Earth in the future.

Meanwhile, amateur astronomers can gather information of their own about 2001 FO32. “The asteroid will be brightest while it moves through southern skies,” said JPL’s Chodas. “Amateur astronomers in the southern hemisphere and at low northern latitudes should be able to see this asteroid using moderate size telescopes with apertures of at least 8 inches in the nights leading up to closest approach, but they will probably need star charts to find it.”

JPL hosts CNEOS for NASA’s Near-Earth Object Observations Program in NASA’s Planetary Defense Coordination Office. The University of Hawaii manages IRTF under contract with NASA. The SpeX instrument was built at the University of Hawaii.

More information about CNEOS, asteroids, and near-Earth objects can be found at:

For more information about NASA’s Planetary Defense Coordination Office, visit:

For asteroid and comet news and updates, follow @AsteroidWatch on Twitter:

5 6 votes
Article Rating
Newest Most Voted
Inline Feedbacks
View all comments
March 12, 2021 2:13 am

Another angle on the orbit of asteroid 2001 FO32.comment image

March 12, 2021 4:03 am

Every week now some asteroid or other – the size of…. – comes close.

Alarmism is big business.

Last edited 1 month ago by fretslider
Reply to  fretslider
March 12, 2021 5:13 am

What was last week’s alarm? The candidates I see at (asteroids passing less than a lunar distance away) seem to have nothing much in Google News.


Reply to  Ric Werme
March 12, 2021 5:32 am

No results found.

Not a lot at all.

Next Week: Chaos of God (an asteroid the size of a Markle ego) will pass by…

Reply to  Ric Werme
March 12, 2021 8:43 am

He prb’ly remembers this recently in the news — Apophis flyby:

Last edited 1 month ago by beng135
Hans Erren
March 12, 2021 4:07 am

Here are the ephemeris, with a maximum magnitude of 11.7 you’ll need a sizeable telescope to see it.

March 12, 2021 4:55 am

During this approach, 2001 FO32 will pass by at about 77,000 mph (124,000 kph) – faster than the speed at which most asteroids encounter Earth. The reason for the asteroid’s unusually speedy close approach is its highly inclined and elongated (or eccentric) orbit around the Sun, an orbit that is tilted 39 degrees to Earth’s orbital plane. This orbit takes the asteroid closer to the Sun than Mercury and twice as far from the Sun as Mars.

I wonder if that 39° inclination is really involved. Oh, I know – the relative speed between the Earth and the asteroid is based on vector difference of the objects’ velocities, and where the asteroid crosses the Earth’s orbital plane the component perpendicular to our plane is at a maximum. So that combined with high aphelion and low perihelion makes for something I’d rather not meet head on.

Reply to  Ric Werme
March 12, 2021 6:29 am

…. I’d rather not meet head on.
How about just a glancing blow?

Energy of just one kg (1kg) of weight at this velocity is huge just over 7.5810^6 GWsec, i.e. about 7.5 million GWsec or 1,200 tons of TNT i.e about 0.8 Hiroshimas/kg.
Just to give an idea, the UK’s electricity load is 40GW, enough energy to power the UK grid for 2 days and 6 hours.
Anyone like to double check, just in case I made a mistake

Last edited 1 month ago by Vuk
Reply to  Vuk
March 12, 2021 9:19 am

One of the more remarkable photos from the Space Shuttle era was of a small pit in a window from a shuttle between flights. They found (some of?) the impactor in the pit – a speck of TiO2, almost certainly paint from a manmade source.

As for your math, that fly-by is some 4-5 times Low Earth Orbital velocity, so that 1 kg mass will have some 20X the kinetic energy of its brother in LEO. Your result feels high, but not enough out of line enough for a real check.

Itdoesn't add up...
Reply to  Vuk
March 12, 2021 10:27 am

77,000x1760x36/39.4/3600 = 34,396m/sec. 0.5mv^2 gives 591.5MJ/kg.
mph x yards/mile x in/yard/in/metre/seconds/hour

Assume a sphere of carbonaceous chondrite of density 2500kg/m^3 of radius 250m, so the mass is 2500x4xπx(250)^3/3 = 163.6 million tonnes

Mulitplying out, and we’re at the order of 100,000x giga x mega joules =10^20J

A Hiroshima bomb is 6×10^13J, so this is about 1.6 million Hiroshima bombs.

Reply to  Itdoesn't add up...
March 12, 2021 11:03 am

Agree, was late for lunch, hurry job, hence double check request, didn’t get speed m/h down to m/sec,

Reply to  Itdoesn't add up...
March 12, 2021 2:48 pm

assumed mass?

In the article they said that spectral analysis might show it as iron (meaning greater mass).

So, maybe showing my ignorance, shouldn’t the mass already be estimated by the speed and orbit, and the size be the unknown variable?

March 12, 2021 5:07 am

No chance it’ll break into two pieces that hit Beijing and DC?

March 12, 2021 6:07 am

This is one speedy lump of rock. Relative to Earth that is. I don’t remember seeing higher.

Tired Old Nurse
March 12, 2021 6:07 am

(Shakes fist at sky) Damn it! SMOD misses again!

March 12, 2021 6:25 am

comment image on Mar 7th.
Asteroid Apophis

Last edited 1 month ago by Krishna Gans
March 12, 2021 7:19 am

Real risk is zipping by overhead. Can it strike twice in DC?

Bruce Cobb
March 12, 2021 7:28 am

Just in case though, Bruce Willis should get a crew together of his old buddies.
Better safe than sorry.

March 12, 2021 7:44 am

How do they know that 95% of the near-Earth asteroids,
the size of 2001 FO32, have been discovered?

Jean Parisot
Reply to  twobob
March 12, 2021 8:24 am

Because they don’t have to worry about reporters with basic math skills.

Reply to  twobob
March 12, 2021 9:24 am

From full sky surveys. A bit of a challenge are objects that have a perihelion near us and a low aphelion as looking for them toward the Sun is more of a challenge than those further out.

OTOH, there are a lot more smaller objects we can’t see, and some of those may surprise us.

March 12, 2021 7:45 am

I was watching a show a few days ago that was attempting to prove that some ancient events could have been caused by a meteor shower.
They mentioned some meteorite cluster, then made the declaration that when they trace back the orbit for 5000 years …
At that point I changed the channel.

March 12, 2021 7:58 am

Apophis is a concern, went by March 6 at 44x Lunar distance. next pass in 2029 caculates ot to one Earth diameter near miss, 0.1 x Lunar distance, unless some ice fizzes off it surface in an unexpected location. But that kind of detail isn’t in the calcs and thinking the calcs are that accurate is just playing with error bars anyway. Its a quarter of a mile across. A hundred megaton warhead detonated about 1/3 of its diameter under its surface, should turn it from a threat into a 20 year cycle meteor shower display.

Itdoesn't add up...
Reply to  DMacKenzie
March 12, 2021 10:52 am

Watch this space:

It is under active observation for refinement of calculation of its orbit. Look for an update next week when the data are in.

Steve Z
Reply to  DMacKenzie
March 12, 2021 12:13 pm

0.1 times lunar distance is about 24,000 miles, or about 3 earth diameters.

Still, that’s much too close for comfort, if the orbital calculations are a little bit off.

Hopefully, we can get our act together by 2029 and shoot it down if necessary. Otherwise we’re in for a lot of global cooling in 2029 (or tsunamis, if it lands in an ocean).

Reply to  Steve Z
March 13, 2021 1:42 pm

oops, cicumference

March 12, 2021 10:02 am

How will this close encounter affect the orb?it of Asteroid 2001 FO32

March 12, 2021 11:20 am

Extraterrestrial Abductions Day is March 20th … coincidence ?

Reply to  Neo
March 12, 2021 2:54 pm

I think not.

March 12, 2021 5:17 pm

I love this website. Nothing more to say, other than fascinating and a learning experience.

%d bloggers like this: