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Would bacteria on incoming meteors burn before impacting?

Would bacteria on incoming meteors burn before impacting?


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I was watching an old Ancient Aliens last night and there was a whole episode dedicated to how the "Gods" (aliens) were spreading disease/plagues.

A good portion of the show was dedicated to how aliens may be sending meteors to Earth with bacteria to spread disease.

Part of this was several scientists talking about an experiment with a rock set in orbit (forgive me that I don't have a link to this). Said rock had many forms of bacteria on it and after a certain amount of time they grabbed the rock and confirmed that some bacteria can survive space conditions.

Then there were other scientists saying that some forms of bacteria/virus may even get worse in zero gravity or space conditions - used salmonella as an example.

But my question is does this even matter? Wouldn't any bacteria or virus colonies on a meteorite just burn up in our atmosphere?


Svante Arrhenius was probably the first scientist to propose the idea of panspermia, that life may have come from, well, that black thing we all have over our heads at night, and all whatever hides behind that dotted blackness.

Since it is genuinely unknown how life appeared, I think your question cannot have any good answer. Yeah, maybe microgravity doesn't seem to be any problem to microbes. Au contraire, those little bugs seem to love microgravity and multiply, and mutate, even faster there than here.

That burning up of a rock in the atmosphere thing would've happened in many different ways, in different angles and speeds throughout the billions of years. The argument is that maybe once or twice… And maybe that's enough. You get a cold once and you got it.


While the surface of a meteor will indeed be pretty sterilised by re-entry, remember that a meteor also has an inside. If it doesn't burn up completely, then parts of the inside may remain cool enough for bacteria/viruses to survive.

The range of environmental conditions life can survive in is incredibly wide, so this is not impossible.


Any bacteria present in a meteor would not necessarily burn. According to the Bad Astronomer's "Bad Addendum" to another unrelated point, "A Meteoric Rise", meteors sure do get extremely hot, but that outside part usually ablates away, leaving the inner part that was extremely cold for who knows how long, which may not have warmed up much during the fall.

Bad Addendum: many people think that a meteorite, after it hits the ground, is very hot and glows red. Actually, meteorites found shortly after impact tend to be warm, but not hot at all! It turns out that it certainly is hot enough to glow while it is in the part of the atmosphere that decelerates it the strongest, but any part that actually melts will be blown off ("ablated") by the wind of its passage. That leaves only the warm part. Even more, the meteor is slowed down so strongly as it moves through the atmosphere that the impact speed is typically only a few hundred kilometers an hour at most. Only the very large (and we're talking meters across) meteors are still moving at thousands of kilometers an hour or more when they impact. Small ones aren't moving that fast at all. Not to say you'd want to be under one: a car in New York was struck by a small meteorite and had a hole punched through it, and the whole back end crushed in. Ouch!

This American Meteor Society resource seems also to indicate that meteorites can fall to the ground without being extremely hot.

  1. Are meteorites “glowing” hot when they reach the ground?

Probably not. The ablation process, which occurs over the majority of the meteorite's path, is a very efficient heat removal method, and was effectively copied for use during the early manned space flights for re-entry into the atmosphere. During the final free-fall portion of their flight, meteorites undergo very little frictional heating, and probably reach the ground at only slightly above ambient temperature.

For the obvious reason, however, exact data on meteorite impact temperatures is rather scarce and prone to hearsay. Therefore, we are only able to give you an educated guess based upon our current knowledge of these events.

This study, "Bacterial Spores Survive Simulated Meteorite Impact", seems to indicate that it's possible, though unlikely, for a bacterium to survive the pressure shock from such an impact.

So it's plausible that an extremophile bacterium could somehow survive this impact by being on the inside of the meteoroid, surviving the ablation process as a meteor, and not even get warmed up to the surrounding atmospheric temperature when it crashes as a meteorite.

There is nothing to indicate that this has actually happened. But what a discovery it would be if something like this were to happen and be confirmed.


Why meteoroids explode before they reach Earth

Our atmosphere is a better shield from meteoroids than researchers thought, according to a new paper published in Meteoritics & Planetary Science.

When a meteor comes hurtling toward Earth, the high-pressure air in front of it seeps into its pores and cracks, pushing the body of the meteor apart and causing it to explode.

"There's a big gradient between high-pressure air in front of the meteor and the vacuum of air behind it," said Jay Melosh, a professor of Earth, Atmospheric and Planetary Sciences at Purdue University and co-author of the paper. "If the air can move through the passages in the meteorite, it can easily get inside and blow off pieces."

Researchers knew that meteoroids often blew up before they reach Earth's surface, but they didn't know why. Melosh's team looked to the 2013 Chelyabinsk event, when a meteoroid exploded over Chelyabinsk, Russia, to explain the phenomenon.

The explosion came as a surprise and brought in energy comparable to a small nuclear weapon. When it entered Earth's atmosphere, it created a bright fire ball. Minutes later, a shock wave blasted out nearby windows, injuring hundreds of people.

The meteoroid weighed around 10,000 tons, but only about 2,000 tons of debris were recovered, which meant something happened in the upper atmosphere that caused it to disintegrate. To solve the puzzle, the researchers used a unique computer code that allows both solid material from the meteor body and air to exist in any part of the calculation.

"I've been looking for something like this for a while," Melosh said. "Most of the computer codes we use for simulating impacts can tolerate multiple materials in a cell, but they average everything together. Different materials in the cell use their individual identity, which is not appropriate for this kind of calculation."

This new code allowed the researchers to push air into the meteoroid and let it percolate, which lowered the strength of the meteoroid significantly, even if it had been moderately strong to begin with.

While this mechanism may protect Earth's inhabitants from small meteoroids, large ones likely won't be bothered by it, he said. Iron meteoroids are much smaller and denser, and even relatively small ones tend to reach the surface.

This research was supported by NASA's Office of Planetary Defense under grant NNX14AL15G.


Why Do Objects Burn as They Enter Earth’s Atmosphere?

One extremely important consideration that goes into the engineering of spaceships is their ability to withstand the heat of reentry. Pushing through the Earth’s atmosphere causes extreme temperatures that can burn up manmade objects and space debris alike. What causes this fiery phenomenon?

1. It’s not about friction, and it’s not about height.
It’s logical to think that friction is the driving force behind all this heat, but in fact it only plays a role closer to the ground where the atmosphere is more dense. Higher up, where meteors streak across the sky and spacecraft return from missions, friction and altitude have very little to do with reentry burning.

2. Velocity is the main factor.
If not friction and height, then what? The answer is velocity and compression. Incoming objects are moving at incredible speeds, and as they do they’re compressing the air in front of them. According to the gas laws of chemistry, compressing a gas heats it up, and there’s a whole lot of compressing going on during reentry. It’s this reaction that causes heat to be generated, and few things can stay intact in that heat unless we make them specifically for the purpose (or they’re way too big, like giant asteroids).

3. This is why heat shields are so important.
NASA has beaten the heat with heat shields, which are designed to withstand the extremes they’re exposed to. Sadly, this doesn’t always avert tragedy. The Columbia space shuttle disaster was a result of a heat shield failure. The shield was damaged and upon reentry, the atmospheric gases broke the shuttle apart.

Trithinium

One extremely important consideration that goes into the engineering of spaceships is their ability to withstand the heat of reentry. Pushing through the Earth’s atmosphere causes extreme temperatures that can burn up manmade objects and space debris alike. What causes this fiery phenomenon?

1. It’s not about friction, and it’s not about height.
It’s logical to think that friction is the driving force behind all this heat, but in fact it only plays a role closer to the ground where the atmosphere is more dense. Higher up, where meteors streak across the sky and spacecraft return from missions, friction and altitude have very little to do with reentry burning.

2. Velocity is the main factor.
If not friction and height, then what? The answer is velocity and compression. Incoming objects are moving at incredible speeds, and as they do they’re compressing the air in front of them. According to the gas laws of chemistry, compressing a gas heats it up, and there’s a whole lot of compressing going onintroducedeentry. It’s this reaction that causes heat to be generated, and few things can stay intact in that heat unless we make them specifically for the purpose (or they’re way too big, like giant asteroids).

3. This is why heat shields are so important.
NASA has beaten the heat with heat shields, which are designed to withstand the extremes they’re exposed to. Sadly, this doesn’t always avert tragedy. The Columbia space shuttle disaster was a result of a heat shield failure. The shield was damaged and upon reentry, the atmospheric gases broke the shuttle apart.


Perseid meteors 2021: All you need to know

View at EarthSky Community Photos. | James Younger caught this colorful meteor on July 26, 2020, over the Salish Sea, from the shores of British Columbia in Canada. Was it a Perseid? The shower was rising to a peak then. The Perseids are known for being colorful. And this meteor is coming from the right direction. So possibly! Thank you, James!

Perseids, beloved summer meteor shower

In the Northern Hemisphere, we rank the August Perseids as an all-time favorite meteor shower of every year. For us, this major shower takes place during the lazy, hazy days of summer, when many families are on vacation. And what could be more luxurious than taking a siesta in the heat of the day and watching this summertime classic in the relative coolness of night? These warm summer nights make meteor watching such a joy.

No matter where you live worldwide, the 2021 Perseid meteor shower will probably produce the greatest number of meteors on the mornings of August 11, 12 and 13. On the peak mornings in 2021, there will be no moonlight to ruin on the show. A non-intrusive waxing crescent phase will beautify the western sky at nightfall, but will set by early-to-mid evening. That guarantees a dark sky for this year’s Perseid meteors.

Here are some thoughts

1. The Perseids tend to be bright, and a good percentage of them should be able to overcome mildly light-polluted skies. Who knows? In a dark sky, you may see up to 60 meteors per hour at the shower’s peak. Will you see over 100 per hour, as in some years? Not likely, perhaps. But you won’t know unless you look …

2. To see more meteors, Try to watch after midnight but before dawn. In a typical year, meteor numbers increase after midnight. Be aware that the Perseid meteors will start to fly in mid-to-late evening from northerly latitudes. South of the equator, the Perseids start to streak the sky around midnight. Here’s an added bonus for evening observing. If fortune smiles upon you, the evening hours might offer you an earthgrazer – a looooong, slow, colorful meteor traveling horizontally across the evening sky. Earthgrazer meteors are rare but memorable. Perseid earthgrazers appear before midnight, when the radiant point of the shower is close to the horizon.

3. Watch in moonlight, but place yourself in the moon’s shadow. The moon’s presence at nightfall and early evening should not be a factor in 2021. But in years when bright moon is overwhelming, there is still a solution. Just place some large structure or natural object – a barn, a cabin, a mountain – between you and the moon. You’ll see more meteors that way than if you’re standing out under the blazing moonlight itself.

4. Consider watching after the peak. People tend to focus on the peak mornings of meteor showers, and that’s entirely appropriate. But meteors in annual showers – which come from streams of debris left behind in space by comets – typically last weeks, not days. Perseid meteors usually start streaking the sky around July 17. We’ll see Perseids for 10 days or so after the peak mornings on August 11, 12 and 13, though at considerably reduced numbers.

Also remember, the Delta Aquariid meteor shower is still rambling along steadily. You’ll see mostly Perseids, but also some Delta Aquariids in the mix. There’s an explanation of how to tell the difference toward the bottom of this article.

Find a dark sky

Looking for a dark area to observe from? Check out EarthSky’s worldwide Best Places to Stargaze map.

The radiant point for the Perseid meteor shower is in the constellation Perseus. But you don’t have to find a shower’s radiant point to see meteors. Instead, the meteors will be flying in all parts of the sky.

Radiant Point of the Perseid Shower

What is the radiant point for the Perseid meteor shower? If you trace all the Perseid meteors backward, they all seem to come from the constellation Perseus, near the famous Double Cluster. Hence, the meteor shower is named in honor of the constellation Perseus the Hero.

However, this is a chance alignment of the meteor shower radiant with the constellation Perseus. The stars in Perseus are light-years distant while these meteors burn up about 60 miles (100 km) above the Earth’s surface. If any meteor survives its fiery plunge to hit the ground intact, the remaining portion is called a meteorite. Few – if any – meteors in meteor showers become meteorites, however, because of the flimsy nature of comet debris. Most meteorites are the remains of asteroids.

In ancient Greek star lore, Perseus is the son of the god Zeus and the mortal Danaë. It is said that the Perseid shower commemorates the time when Zeus visited Danaë, the mother of Perseus, in a shower of gold.

From mid-northern latitudes, the constellation Perseus, the stars Capella and Aldebaran, and the Pleiades cluster light up the northeast sky in the wee hours after midnight on August nights. The meteors radiate from Perseus. Photo: Till Credner, AlltheSky.com Here’s a cool binocular object to look for while you’re watching the meteors. The constellation Cassiopeia points out the famous Double Cluster in the northern tip of the constellation Perseus. Plus, the Double Cluster nearly marks the radiant of the Perseid meteor shower. Image via Flickr/ madmiked.

Suggestions for making the most of the Perseids

General rules for Perseid-watching. No special equipment, or knowledge of the constellations, needed.

Find a dark, open sky to enjoy the show. An open sky is essential because these meteors fly across the sky in many different directions and in front of numerous constellations.

Give yourself at least an hour of observing time, because the meteors in meteor showers come in spurts and are interspersed with lulls. Remember, your eyes can take as long as 20 minutes to adapt to the darkness of night. So don’t rush the process.

Know that the meteors all come from a single point in the sky. If you trace the paths of the Perseid meteors backwards, you’d find they all come from a point in front of the constellation Perseus. Don’t worry about which stars are Perseus. Just enjoying knowing and observing that they all come from one place on the sky’s dome.

Enjoy the comfort of a reclining lawn chair. Bring along some other things you might enjoy also, like a thermos filled with a hot drink.

Remember … all good things come to those who wait. Meteors are part of nature. There’s no way to predict exactly how many you’ll see on any given night. Find a good spot, watch, wait.

Composite of 12 images acquired on August 13, 2017, by Felix Zai in Toronto. He wrote: “Perseid meteor shower gave a good show even though the moonlight drowned out most of the fainter ones. A huge fireball was captured in this photo.” Thanks, Felix! By the way, it’s only in a meteor “storm” that you’d see this many meteors at once. Even in a rich shower, you typically see only 1 or 2 meteors at a time.

Source of the Perseid meteor shower

What’s the source of the Perseid meteor shower? Every year, from around July 17 to August 24, our planet Earth crosses the orbital path of Comet Swift-Tuttle, the parent of the Perseid meteor shower. Debris from this comet litters the comet’s orbit, but we don’t really get into the thick of the comet rubble until after the first week of August. The bits and pieces from Comet Swift-Tuttle slam into the Earth’s upper atmosphere at some 130,000 miles (210,000 km) per hour, lighting up the nighttime with fast-moving Perseid meteors.

If our planet happens to pass through an unusually dense clump of meteoroids – comet rubble – we’ll see an elevated number of meteors. We can always hope!

Comet Swift-Tuttle has a very eccentric – oblong – orbit that takes this comet outside the orbit of Pluto when farthest from the sun, and inside the Earth’s orbit when closest to the sun. It orbits the sun in a period of about 133 years. Every time this comet passes through the inner solar system, the sun warms and softens up the ices in the comet, causing it to release fresh comet material into its orbital stream.

Comet Swift-Tuttle last reached perihelion – closest point to the sun – in December 1992 and will do so next in July 2126.

The Perseids happen every year. Their parent comet – Swift-Tuttle – takes about 130 years to orbit the sun once. It last rounded the sun in the early 1990s and is now far away. But we see the Perseids each year, when Earth intersects the comet’s orbit, and debris left behind by Swift-Tuttle enters our atmosphere. Chart via Guy Ottewell.

Bottom line: The 202 Perseid meteor shower is expected to produce the most meteors in the predawn hours of August 11, 12 and 13, in a dark, moonless sky. Here’s how to get the most from this year’s shower.


ANCIENT CRUST

The oldest known impact structures in the world are located in Australia and North America. These regions contain some of the most ancient continental crust in the world, with certain areas containing rock that dates back 4.4 billion years—pre-dating the evolution of life and the formation of the Moon. Because they rarely experience earthquakes or volcanism, they have preserved impact craters spanning hundreds of millions of years.

Impact craters are found worldwide, ranging from less than 1 kilometer to over 300 kilometers across. Interest in the discovery and identification of these structures has bloomed in the past 100 years, with the rate of discovery corresponding with increased interest in space exploration, as well as mounting geological evidence that ancient asteroids played an enormous role in creating the Earth as we know it.

Ψ THE POPIGAI CRATER

Location: The Gulf of Mexico | Size: 100 km | Age: 66 million years

The Chixculub Impact is widely considered by scientists to have been the primary cause of the K-T extinction event, which resulted in the end of the dinosaurs 66 million years ago.

Location: Siberia, Russia | Size: 100 km | Age: 35 million years

The Popigai crater is linked to the Eocene–Oligocene extinction event, which occurred about 34 million years ago and was marked by the rapid cooling of the Earth.

Location: Western Australia | Size: 100 km | Age: 2.229 billion years

The Yarrabubba Crater is the oldest confirmed impact crater on Earth. It is thought that the impact, which occurred at the end of a period of glaciation (”Snowball Earth”), contributed to the rapid warming of the planet following an extended ice age.

Ψ THE YARRABUBBA CRATER

Ψ THE CHIXCULUB CRATER


We see videos of meteors falling, burning bright, ets. However they appear to always travel at a steep angle. Is there a reason why meteors can not fall to the earth at a perfect perpendicular to the earths surface?

/u/Astrokiwi covered the orbital mechanics side of this question, but it's worth thinking about what meteors coming in from different directions look like to a viewer on the ground.

Here's a long-duration, whole-sky photo of a meteor shower:

The center of the photo is straight up the horizon is on the edges. This photo was taken at a time and place where the meteors were indeed coming in almost perpendicular to the Earth's surface (about 75 degrees angle, actually). All the meteors are coming in on parallel tracks, but because of perspective they appear to be radiating out from a single point near the center of the picture. It's a bit like how parallel railroad tracks seem to meet at a vanishing point, or seeing snowflakes as you drive through a snowstorm.

The meteors that are coming directly toward the observer appear as very short streaks near the center of this image. To the eye, they look like a sudden stationary flash of light in the sky, or a brief slow-moving dot. They're directly overhead, where people tend not to look, and they're not very noticeable anyway. The much more obvious streaks closer to the horizon are caused by meteors that are also coming almost straight down perpendicular to the surface of the Earth, but are aimed at a spot maybe 100 km away from the observer.

And there's one last factor to consider: meteors that come straight down into the atmosphere reach the thick parts of the atmosphere very quickly, and burn up in just a second or two. Meteors that come in at a glancing angle spend more time in the upper atmosphere and take longer to burn up -- long enough for someone to notice, pull out their cell phone and take a video.

The upshot: meteors do come in perpendicular to the Earth's surface, but:

the ones that come in directly over the observer are hard to notice

the ones that don't come in directly over the observer don't look like youɽ expect

the ones that come in at a glancing angle last longer, and so are much easier to notice and photograph.


The When & Where: Eta Aquariids Peak

Meteor showers are very predictable events, so astronomers know exactly when you have the best chance of seeing them.

The shower is forecast to peak on the morning of Friday, May 6th, with good activity from the 4th through the 8th. Counts typically range from 10-20 meteors per hour, averaging around 10. In 2021, the peak of the Eta Aquariids is expected just before sunrise on Friday, May 6th.

In the case of the Eta Aquarids, the radiant doesn’t rise until long after midnight, and it reaches its highest in the sky well after sunrise. So the best time to watch for meteors is anywhere from one to two hours before sunrise. Earlier than that, the radiant is too low — any later, the sky is too bright. You can use an AR app like Night Sky on your smartphone to track down the constellation.


Circulation

The circulation of the atmosphere occurs due to thermal differences when convection becomes a more efficient transporter of heat than thermal radiation. On planets where the primary heat source is solar radiation, excess heat in the tropics is transported to higher latitudes. When a planet generates a significant amount of heat internally, such as is the case for Jupiter, convection in the atmosphere can transport thermal energy from the higher temperature interior up to the surface.


Would bacteria on incoming meteors burn before impacting? - Astronomy

What would happen to life on Earth if the Sun were to burn out how long would we be able to survive?

The Earth's atmosphere has some capacity to hold in heat but not much of one. A relatively simple calculation would show that the Earth's surface temperature would drop by a factor of two about every two months if the Sun were shut off. The current mean temperature of the Earth's surface is about 300 Kelvin (K). This means in two months the temperature would drop to 150K, and 75K in four months. To compare, the freezing point of water is 273K. So basically it'd get too cold for us humans within just a few weeks. Some bacteria seem to be capable of surviving at extremely cold temperatures in space, so there would probably still be some limited bacterial life left on Earth. But anything else would die pretty quickly (even the rats :).

We could probably survive if we went deep underground where the Earth's internal heat is higher or if we built totally isolated habitation domes, but at the moment I don't think we're capable of something like that on any appreciable scales.

About the Author

Marko Krco

Marko has worked in many fields of astronomy and physics including planetary astronomy, high energy astrophysics, quantum information theory, and supernova collapse simulations. Currently he studies the dark nebulae which form stars.


Effects of Ancient Meteor Impacts Still Visible on Earth Today

More than 35 million years ago, a 15-story wall of water triggered by an asteroid strike washed over Virginia from its coast, then located at Richmond, to the foot of the inland Blue Ridge Mountains — an impact that would affect millions of people should it occur today. Yet despite its age, the effects of this ancient asteroid strike, as well as other epic space rock impact scars, can still be felt today, scientists say.

The Virginia impact site, called the Chesapeake Bay Crater, is the largest known impact site in the United States and the sixth largest in the world, said Gerald Johnson, professor emeritus of geology at the College of William and Mary in Virginia. Despite its size, clues about the crater weren't found until 1983, when a layer of fused glass beads indicating an impact were recovered as part of a core sample. The site itself wasn't found until nearly a decade later. [When Space Attacks: The 6 Craziest Impacts]

The comet or asteroid that caused the impact, and likely measured 5 to 8 miles (8 to 13 kilometers) in diameter, hurtled through the air toward the area that is now Washington, D.C., when it fell. The impact crated a massive wave 1,500 feet (457 meters) high, researchers said.

Though the impactor left a crater about 52 miles across and 1.2 miles deep (84 km across and 1.9 km deep), the object itself vaporized, Johnson explained.

"I'm just sad we can't have a piece of it," Johnson said in a statement.

Modern effects

But the effects of the asteroid impact can still be seen today, most notably in the bay itself. Until 18,000 years ago, the bay region was dry. A giant ice sheet then covered North America, and when it began melting 10,000 years ago, valleys flooded, including the depression formed by the crater.

The ancient impact still affects the region today, in the form of land subsidence, river diversion, disruption of coastal aquifers and ground instability.

Last February, an meteor explosion over the Russian city of Chelyabinsk confirmed that the Chesapeake Bay impactor wasn't the only space rock out there aimed at Earth. Though the Chelyabinsk asteroid was only about 56 feet (17 m) in diameter, it injured more than 1,000 people and caused millions of dollars in structural damage.

"That asteroid still had a major effect on the ground, and there are potentially millions of them," Dan Mazanek, a near-Earth object (NEO) expert at NASA's Langley Research Center in Virginia, said in the statement. "Another meteor of similar size to that would be the next likely event."

Finding NEOs

Every day, small objects pass near Earth or burn up in the planet's atmosphere. Objects about 50 miles (80 km) across pass within a few lunar distances on a monthly or annual basis without being drawn in by the planet's gravity.

"The frequency is always a question," Mazanek said. "We know that the larger objects are less frequent, but they have more devastating effects."

According to models, scientists have discovered only about 10 percent of the objects larger than 328 feet (100 m), leaving many potentially threatening asteroids that pose a threat to the Earth still unknown.

Both telescope and radar are instrumental in searching for incoming objects. NASA's Near-Earth Object Program is one of the groups watching for potentially dangerous incoming objects. Mazanek said the program has been responsible for about 99 percent of all NEO discoveries since 1998.

Knowing where to point the instruments is a challenge. Timing, too, is tricky. A 100-year impact event doesn't mean that 100 years will pass before the event occurs again.

"It's not like a bus or a train schedule it just happens that frequently on average," Mazanek said. "It's like a coin toss. Even though it's a 50-50 heads or tails average, it could be heads 10 times in a row or tails 10 times in a row."


This NASA Mission May Cause an Artificial Meteor Shower

A study says the DART mission’s collision with an asteroid near Earth may liberate enough debris to reach Earth’s atmosphere.

If all goes to plan, in September 2022 a NASA spacecraft, the Double Asteroid Redirection Test mission or DART, will slam into a space rock with the equivalent energy of three tons of TNT. The goal is to nudge the orbit of its target object ever-so-slightly, a practice run to see if we could divert an asteroid from a catastrophic impact with our planet in the future.

The impact on that asteroid could produce the first meteor shower ever to result from human activities in space, according to a paper published earlier this year in The Planetary Science Journal. Observing the shower could let scientists on Earth study the composition of near-Earth asteroids. But this cloud of debris would also mark a small irony for a space mission that has a goal of helping to protect our planet.

If this small shower of space rocks reaches our planet, it will create a minuscule amount of peril for orbiting satellites. Although the risk is tiny, the study’s author says, anticipating the effects of the spacecraft’s operations could establish a template for future space missions to minimize their impacts on Earth and the commons of space through which it travels.

NASA plans to launch the 1,100-pound DART spacecraft in 2021. Its target is Didymos, a pair of near-Earth asteroids that travel around the sun together. DART is aiming for the smaller of the two, affectionately named Didymoon, which measures about 535 feet across and orbits the larger asteroid. The force of the impact is expected to change Didymoon’s 11.92-hour orbit by about 4 minutes, a big enough change for telescopes on Earth to detect. If it succeeds, the mission might help confirm that humanity’s best defense against a rogue asteroid is to bump it into another orbit away from Earth.

Didymos makes regular passes of our planet at a minimum of 4 million miles — or 16 times the Earth-moon distance — approximately every 20 years. Its next close pass is scheduled for Oct. 4, 2022, at a distance of about 6.6 million miles, just after DART is scheduled to impact on Sept. 30, making observations from Earth easier.

The impact is expected to produce between 22,000 and 220,000 pounds of centimeter-sized debris.

“There’s a fair amount of material that will be ejected,” said Paul Wiegert, the paper’s author and an astronomy professor at the University of Western Ontario.

Most of the wreckage should be ejected at less than about 2,000 miles per hour and will follow the orbit of the asteroid, with no chance of reaching Earth for thousands of years. If some of the debris reaches more than about 13,000 miles per hour, which will depend on the structure of the asteroid and the angle of impact, it could make the relatively short jump to Earth, in as little as 15-30 days.

The amount of material that could reach Earth is modest Dr. Wiegert estimates perhaps a few grams, resulting in only “a few to ten” meteors visible in our night sky over a few days. But that could be enough to learn more about the composition of the asteroid as the meteors disintegrate.

“When they burn out, they emit some light,” said Audrey Bouvier, a planetary scientist from the University of Bayreuth in Germany. And by analyzing the spectrum of that light, Dr. Bouvier says it is possible to “establish which elements were present.”

The prospect that any of this debris will damage Earth orbiting satellites is negligible. Tom Statler, the program scientist for DART at NASA, says the team’s own analysis shows there is “no significant debris hazard.”

But however remote the risks from the DART mission, Dr. Wiegert and other astronomers suggest that it will set an important precedent.

Aaron Boley, a planetary astronomer at the University of British Columbia, notes this would be the first time human activity on an asteroid ejects debris that reaches Earth.

“Space is big, but what we do in space can affect us,” he said.

Future human activities in space, such as near-Earth asteroid mining and further planetary defense testing, could shed more material that arrives in Earth’s orbit. That means the DART mission might be an opportunity to consider how human activities in deep space affect life on and around Earth.

“There’s an opportunity here for a clear demonstration of astro-environmental stewardship,” Dr. Boley said.

Dr. Boley suggests that changes to the DART mission could avert debris reaching Earth in that 15- to 30-day time frame and set a precedent for future asteroid activities. According to Dr. Wiegert’s calculations, if the impact occurs outside of a window one week before or after the asteroid’s closest approach with Earth on Oct. 4, no material would cross the planet’s path this quickly.

“If it’s the case that launching it two weeks later or earlier does not have any additional operational effect on the mission, then it would be worth it to set the precedent,” Dr. Boley said.

Dr. Statler, however, says the timing of the impact is “dictated by orbital dynamics and communication with Earth,” and the planned impact date also allows for optimal viewing by ground-based observatories, so it would not be feasible to reschedule it.

While DART poses no meaningful risk, Dr. Wiegert says future asteroid missions should take the debris issue into account, just as missions closer to Earth need to better plan for space junk they leave in orbit. “It’s the first of a possibly large number of meteoroid streams we might create in the solar system that could become a hazard,” he said.



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