Thanks everybody for the great, through-provoking questions, we had a lot of fun and you got us thinking! That's all we have time for right now, but this was such a nice way to interact with you interesting people! We will login tomorrow to answer anymore questions that come in. While we were doing this the International Astronomical Union released the name for the asteroid we are targeting: Dimorphos!

Next week is [Asteroid Day]( where we raise awareness about the rocks that regularly zoom past Earth. We are a bunch of European Space Agency (ESA) experts on asteroids here to answer any questions you may have, from dinosaur extinction to asteroid mining and even deflection!

We are:

Paolo Martino – I am ESA’s system engineer for Hera that will be launched in 2024 to study what happens when NASA's DART hits the Didymos Asteroid. We hope to prove humankind can actually deflect an asteroid. Originally from Italy, I spent more than ten years at ESA’s technical heart ESTEC working on several satellites. I have worked on the Hera mission since 2012. I can also answer any questions in Italian. (PM)

Marco Micheli – I am an Italian astronomer, my job is to observe asteroids that may be dangerous to our planet and calculate the risk they pose. I started doing this as an amateur astronomer when I was 16, and then, after a degree in physics and a PhD in Hawaii I was able to turn asteroid hunting into my daily job at ESA's Near-Earth Object Coordination Centre. Our observations, taken with some of the largest and most powerful telescopes in the world, allow us to measure the position and trajectory of potentially dangerous asteroids, and predict close passages and possible collisions with our planet. I can answer your questions in Italian too. (MM)

Heli Greus – I am ESA’s Hera product assurance and safety manager making sure that after NASA’s DART probe hits Didymos we launch the Hera probe to observe what happens next and map the resulting impact crater after the dust has settled. We will also launch two CubeSats to fly closer to the asteroid's surface. With all this information we can hopefully deflect asteroids that are a threat for humankind. I grew up in Finland but have been working at ESA’s technical heart in The Netherlands for 13 years. Feel free to ask questions in Suomi too! (HG)

Detlef Koschny – I am co-managing the Planetary Defence Office, part of ESA’s Space Safety programme that is working to protect our planet from asteroids, violent solar outbursts and the build-up of dangerous space debris. I have a passion for cosmic dust, meteors, fireballs, and other minor bodies in the solar system, in particular asteroids. I have worked on many planetary missions. Recently, I was involved in a study where we took videos of the surface of our European laboratory on the International Space Station to understand how many micro-meteoroids hit our module. Originally from Germany and now living in the Netherlands, I can answer questions in German and hopefully in Dutch, too. (DVK)

Aidan Cowley – Science Advisor for ESA and materials scientist working on human spaceflight and exploration, including in-situ resource utilisation to enable sustained exploration of other worlds (and asteroids!) by using resources available in space. For example we developed [3d-printing from lunar regolith to build a moon base ( (AC)

Comments: 318 • Responses: 55  • Date: 

MartinMorgen135 karma

I always wanted to ask: what is worse for life on Earth - to be hit by a single coalesced asteroid chunk, or to be hit by a multiple smaller pieces of exploded asteroid, aka disrupted rubble pile scenario?

ESA_Asteroid_Day129 karma

DVK: This is difficult to answer. If the rubble is small (centimetres to meters) it is better to have lots of small ones – they’d create nice bright meteors. If the rubble pieces are tens of meters it doesn’t help.

makabis101 karma

Can we really detect any asteroids in space with accuracy and do we have any real means of destroying it?

ESA_Asteroid_Day141 karma

Yes, we can detect new asteroids when they are still in space. Every night dozens of new asteroids are found, including a few that can come close to the Earth.

Regarding the second part of the question, the goal would be to deflect them more than destroy them, and it is technologically possible. The Hera/DART mission currently being developed by ESA and NASA will demonstrate exactly this capability.


IndigoImperatrix82 karma

Would the public be informed if an impending asteroid event were to happen?

And, how would the extinction play out? Bunch of people crushed to death, knocked off our orbit, dust clouds forever?

ESA_Asteroid_Day135 karma

DVK: We do not keep things secret – all our info is at the web page The ‘risky’ objects are in the ‘risk page’. We also put info on really close approaches there. It would also be very difficult to keep things ‘under cover’ – there are many high-quality amateur astronomers out there that would notice.

Robertdigitalorgasm61 karma

Let’s say that hypothetically, an asteroid the size of Rhode Island is coming at us, it will be a direct hit - you’ve had the resources and funding you need, your plan is fully in place, everything you’ve wanted you got. The asteroid will hit in 10 years, what do you do?

ESA_Asteroid_Day96 karma

DVK: I had to look up how big Rhode Island is – a bit larger than the German Bundesland ‘Saarland’. Ok – this would correspond to an object about 60 km in diameter, right? That’s quite big – we would need a lot of rocket launches, this would be extremely difficult. I would pray. The good news is that we are quite convinced that we know all objects larger than just a few kilometers which come close to our planet. None of them is on a collision course, so we are safe.

CourteousBear33 karma

Why are you quite convinced that you know all object of that size? And what is your approach in finding new celestial bodies?

ESA_Asteroid_Day56 karma

DVK: There was a scientific study done over a few years (published in Icarus 2018, search for Granvik) where they modelled how many objects there are out there. They compared this to the observations we have with the telescopic surveys. This gives us the expected numbers shown here on our infographic:

There are additional studies to estimate the ‘completeness’ – and we think that we know everything above roughly a few km in size.

To find new objects, we use survey telescopes that scan the night sky every night. The two major ones are Catalina and Pan-STARRS, funded by NASA. ESA is developing the so-called Flyeye telescope to add to this effort

CourteousBear10 karma

Thanks for the answer, that's really interesting! It's also funny that the fist Flyeye deployed is in Sicily, at less than 100km from me, I really had no idea

ESA_Asteroid_Day11 karma

DVK: Indeed, that's cool. Maybe you can go and visit it one day.

Kflynn13377 karma

What about Interstellar objects however, like Oumuamua?

ESA_Asteroid_Day13 karma

DVK: The two that we have seen - 'Oumuamua and comet Borisov - were much smaller than the Saarland (or Rhode Island ;-) - not sure about Borisov, but 'Oumuamua was a few hundred meters in size. So while they could indeed come as a complete surprise, they are so rare that I wouldn't worry.

MartinMorgen41 karma

In 2029 asteroid Apophis will fly really close to Earth, even closer than geostationary satellites. Can we use some of those satellites to observe the asteroid? Is it possible to launch very cheap cube sats to flyby Apophis in 2029?

ESA_Asteroid_Day58 karma

DVK: Yes an Apophis mission during the flyby in 2029 would be really nice. We even had a special session on that topic at the last Planetary Defense Conference in 2019, and indeed CubeSats were mentioned. This would be a nice university project – get me a close-up of the asteroid with the Earth in the background!

funkballzthachurlish2 karma

So you’re saying it was discussed and shelved?

ESA_Asteroid_Day4 karma

In the conference we just presented ideas. To make them happen needs funding - in the case of ESA the support of our member countries. But having something presented at a conference is the first step. One of the results of the conference was a statement to space agencies to consider embarking on such a mission. See here:

Go to the section 'resolutions'. This is now a statement that scientists can use to present to their funding agencies, demonstrating that it's not just their own idea.

xenixesa39 karma

There must be a trade-off when targeting asteroids as they get closer to Earth, is there a rule of thumb at what the best time is to reach them, in terms of launch time versus time to reach the asteroid and then distance from Earth?

ESA_Asteroid_Day44 karma

DVK: Take e.g. a ‘kinetic impactor’ mission, like what DART and Hera are testing. Since we only change the velocity of the asteroid slightly, we need to hit the object early enough so that the object has time to move away from it’s collision course. Finding out when it is possible to launch requires simulations done by our mission analysis team. They take the strength of the launcher into account, also the available fuel for course corrections, and other things. Normally each asteroid has its own best scenario.

plognog38 karma

I'm sure you've been asked this many times but how realistic is the plot of Armageddon? How likely is it that our fate as a species will rely on (either) Bruce Willis / deep sea oil drillers?

ESA_Asteroid_Day76 karma

Taking into consideration that Bruce Willis is now 65 and by the time HERA is launched he will be 69, I do not think that we can rely on him this time (although I liked the movie).

HERA will investigate what method we could use to deflect asteroid and maybe the results will show that we indeed need to call the deep sea oil drillers.


ForkShirtUp19 karma

So then would it be easier to train oil drillers to become astronauts, or to train astronauts to be oil drillers?

ESA_Asteroid_Day41 karma

I do not know which one would be easier since I have no training/experience of deep see oil drilling nor becoming an astronaut, but as long as the ones that would go to asteroid have the sufficient skills and training (even Bruce Willis), I would be happy.


Oukasagetsu37 karma

Will 2020's climax be a really big rock?

ESA_Asteroid_Day40 karma

DVK: Let's hope not...

plognog31 karma

Thanks for doing this AMA! Did we know the Chelyabinsk meteor in 2013 (the one which had some great videos on social media) was coming? Ig not, how comes?

Also, as a little side one, have there been any fatalities from impact events in the past 20 years?

ESA_Asteroid_Day46 karma

Unfortunately, the Chelyabinsk object was not seen in advance, because it came from the direction of the Sun where ground-based telescopes cannot look.

No known fatalities from impacts have happened in the past 20 years, although the Chelyabinsk event did cause many injuries, fortunately mostly minor.


voidshaper15 karma

How often do impacts from that direction happen, compared to impacts from visible trajectories?

ESA_Asteroid_Day26 karma

In terms of fraction of the sky, the area that cannot be easily scanned from the ground is roughly a circle with a radius of 40°-50° around the current position of the Sun, corresponding to ~15% of the total sky. However, there is a slight enhancement of objects coming from that direction, therefore the fraction of objects that may be missed when heading towards us is a bit higher.

However, this applies only when detecting an asteroid in its "final plunge" towards the Earth. Larger asteroids can be spotted many orbits earlier, when they are farther away and visible in the night side of the sky. Their orbits can then be determined and their possible impacts predicted even years or decades in advance.


brodiebt120 karma

Do you also look at protecting the moon from asteroids? Would an impact of a large enough scale potentially have major impacts on the earth?

ESA_Asteroid_Day16 karma

DVK: There are programmes that monitor the Moon and look for flashes from impacting small asteroids (or meteoroids) - or the Spanish MIDAS project. We use the data to improve our knowledge about these objects. These programmes just look at what is happening now.

For now we would not do anything if we predicted a lunar impact. I guess this will change once we have a lunar base in place.

Chrizzee_Hood18 karma

After proving to be able to land on one, could an asteroid serve as a viable means to transport goods and or humans throughout the solar system when the orbit of said asteroid prooves benificial. While it is probably quite problematic to land the payload, it could save fuel or am I mistaken?

ESA_Asteroid_Day21 karma

Neat idea! Wonder if anyone has done the maths on the amount of fuel you would need/save vs certain targets. - AC

ESA_Asteroid_Day24 karma

PM: To further complement, the saving is quite marginal indeed because in order to land (softly) on the asteroid you actually need to get into the very same orbit of that asteroid . At that point your orbit remains the same whether you are on the asteroid or not..

MartinMorgen18 karma

Why aren't there an international organisation comprised of countries focused on the asteroid defence? Imagine like the organisation with multi-billion $ budget and program of action on funding new telescopes, asteroid exploration mission, plans for detection of potentially dangerous NEA, protocols on action after the detection - all international, with heads of states discussing these problems?

ESA_Asteroid_Day26 karma

DVK: There are international entities in place, mandated by the UN: The International Asteroid Warning Network ( and the Space Mission Planning Advisory Group ( These groups advise the United Nations. That is exactly where we come up with plans and protocols on action. But: They don’t have budget – that needs to come from elsewhere. I am expecting that if we have a real threat, we would get the budget. Right now, we don’t have a multi-billion budget.

sphinxJim15 karma

By how much is DART expected to deflect Didymos?

Do we have any indication of the largest size of an asteroid we could potentially deflect?

ESA_Asteroid_Day16 karma

PM: Didymos is a binary asteroid, consisting of a main asteroid Didymos A (~700m) and a smaller asteroid Didymos B (~150m) orbiting around A with a ~12 hours period. DART is expected to impact Didymos B and change its orbital period w.r.t. Didymos A of ~1%. (8 mins)

The size of Didymos B is the most representative of a potential threat to Earth (the highest combination of probability and consequence of impacts), meaning smaller asteroids hit the Earth more often but have less severe consequences, larger asteroids can have catastrophic consequences but their probability of hitting the earth is very very low.

stinkinbutthole7 karma

Why is there less probability of larger asteroids hitting earth?

ESA_Asteroid_Day12 karma

DVK: There are less large objects out there. The smaller they are, the more there are.

FrostyPosition401215 karma

If budget was no object, which asteroid would you most like to send a mission to?

ESA_Asteroid_Day24 karma

Not sure if it counts as an asteroid, but Detlef and myself would probably choose ʻOumuamua, the first discovered interstellar object.


DirtyPolecat9 karma

Do we even have the capability to catch up to something like that screaming through our solar system? That thing has to have a heck of a velocity to just barrel almost straight through like that.

ESA_Asteroid_Day7 karma

DVK: Correct, that would be a real challenge. We are preparing for a mission called 'Comet Interceptor' that is meant to fly to an interstellar object or at least a fresh comet - but it will not catch up with it, it will only perform a short flyby.

ESA_Asteroid_Day16 karma

Nice question! For me, I'd be looking at an asteroid we know something about, since I would be interested in using it for testing how we could extract resources from it. So for me, I would choose Itokawa (, which was visited by Hayabusa spacecraft. So we already have some solid prospecting carried out for this 'roid! - AC

KurraKatt14 karma

I've heard that some asteroids contains large amounts of iron. Is there a possibility that we might have "space mines" in the far away future, if our own supply if iron runs out?

ESA_Asteroid_Day12 karma

Yes, this is a topic in the field known as space mining, part of what we call Space Resources. In fact, learning how we can process material we might find on asteroids or other planetary bodies is increasingly important, as it opens up the opportunities for sustainable exploration and commercialization. Its a technology we need to master, and asteroids can be a great target for testing how we can create space mines :) - AC

SkaroHigh12 karma

President Obama wanted to send a crewed spacecraft to an asteroid - in your opinion is this something that should still be done in the future, would there be any usefulness in having a human being walk/float on an asteroid's surface?

ESA_Asteroid_Day14 karma

DVK: It would definitely be cool. I would maybe even volunteer to go. Our current missions to asteroids are all robotic, the main reason is that it is much cheaper (but still expensive) to get the same science. But humans will expand further into space, I am sure. If we want to test human exploration activities, doing this at an asteroid would be easier than landing on a planet.

ESA_Asteroid_Day12 karma

Yes, but I am slightly biased by the fact that I work at the European astronaut centre ;) There exist many similarities to what we currently do for EVA (extra vehicular activities) operations on the International Space Station versus how we would 'float' around an asteroid. Slightly biased again, but using such a mission to test exploration technologies would definitely still have value. Thanks Obama! - AC

AliceTrippDaGain11 karma

What are your favourite sci-fi series?

ESA_Asteroid_Day24 karma

Big fan of The Expanse at the moment. Nice, hard sci-fi that has a good impression of being grounded in reality - AC

ESA_Asteroid_Day10 karma

DVK: My favorites are ‘The Expanse’, I also liked watching ‘Salvation’. For the first one I even got my family to give me a new subscription to a known internet streaming service so that I can see the latest episodes. I also loved ‘The Jetsons’ and ‘The Flintstones’ as a kid. Not sure the last one counts as sci-fi though. My long-time favorite was ‘Dark Star’ .

ESA_Asteroid_Day7 karma

When I was a kid I liked The Jetsons, when growing up Star Trek, Star wars and I also used to watch with my sister the 'V'.


Trung_gundriver9 karma

can the current anti-ballistic missiles systems intercept a terminal phase earth strike asteroid? or it is better to know beforehand and launch an impacting vehicle into space?

ESA_Asteroid_Day10 karma

DVK: While I do see presentations on nuclear explosions to deflect asteroids at our professional meetings, I have not seen anybody yet studying how we could use existing missile systems. So it's hard to judge whether existing missiles would do the job. But in general, it is better to know as early as possible about a possible impact and deflect it as early as possible. This will minimize the needed effort.

voidshaper9 karma

When determining the potential threat of a NEA, is the mass of an object a bigger factor or size? I'm asking because I'm curious if a small but massive object (say, with the density of Psyche) could survive atmospheric entry better than a comparatively larger but less massive object.

ESA_Asteroid_Day14 karma

The mass is indeed what really matters, since it’s directly related with the impact energy.

And as you said composition also matters, a metal object would survive atmospheric entry better, not just because it’s heavier, but also because of its internal strength.


Freemening8 karma

How much are we prepared against asteroid impacts at this moment?

ESA_Asteroid_Day10 karma

DVK: 42… :-) Seriously – I am not sure how to quantify ‘preparedness’. We have international working groups in place, mentioned earlier (search for IAWN, SMPAG). We have a Planetary Defence Office at ESA, a Planetary Defense Office at NASA (who spots the difference?), search the sky for asteroids, build space missions… Still we could be doing more. More telescopes to find the object, a space-based telescope to discover those that come from the direction of the Sun. Different test missions would be useful, … So there is always more we could do.

SirMcWaffel8 karma

Have you got any data on the NEO coverage? Is there estimations on the percentage of NEOs we have detected and are tracking? How can we improve the coverage? How many times have asteroids been able to enter earths atmosphere without being detected beforehand?

ESA_Asteroid_Day5 karma

Here’s our recently updated infographics with the fraction of undiscovered NEOs for each size range:

As expected, we are now nearly complete for the large ones, while many of the smaller ones are still unknown.

In order to improve coverage, we need both to continue the current approach, centered on ground-based telescopes, and probably also launch dedicated telescopes to space, to look at the fraction of the sky that cannot be easily observed from the ground (e.g., towards the Sun).

Regarding the last part of your question, small asteroids enter the Earth atmosphere very often (the infographics above gives you some numbers), while larger ones are much rarer.

In the recent past, the largest one to enter our atmosphere was about 20 meters in diameter, and it caused the Chelyabinsk event in 2013. It could not be detected in advance because it came from the direction of the Sun.

We have however detected a few small ones before impact. The first happened in 2008, when a ~4-meter asteroid was found to be on a collision course less than a day before impact, it was predicted to fall in Northern Sudan, and then actually observed falling precisely where (and when) expected.


ESA_Asteroid_Day1 karma


DVK: And to add what MM said - Check out There is a ‘discovery statistics’ section which provides some of the info you asked about. NASA is providing similar information here To see the sky which is currently covered by the survey telescopes, you need to service of the Minor Planet Center which we all work together with:, ‘observers’, ‘sky coverage’. That is a tool we use to plan where we look with our telescopes, so it is a more technical page.

ForbesDawson18957 karma

Considering NASA, ESA, IAU etc. is working hard to track Earth-grazing asteroids, how come the Chelyabinsk object that airburst over Russia in 2013 came as a total surprise?

ESA_Asteroid_Day6 karma

The Chelyabinsk object came from the direction of the Sun, where unfortunately ground-based telescopes cannot look at. Therefore, it would not have been possible to discover it in advance with current telescopes. Dedicated space telescopes are needed to detect objects coming from this direction in advance.


MartinMorgen7 karma

Are there any automatic systems for checking large numbers of asteroids orbits, to see if the asteroid's orbit is coming dangerously close to Earth, or is it done by people individually for every asteroid? I ask it because LSST Rubin is coming online soon and you know it will discover a lot of new asteroids.

ESA_Asteroid_Day9 karma

Yes, such systems exist, and monitor all known and newly discovered asteroids in order to predict possible future impacts.

The end result of the process is what we call "risk list":

It is automatically updated every day once new observational data is processed.


the-player-of-games5 karma

What is the process to determine the orbit of a newly discovered asteroid?

ESA_Asteroid_Day4 karma

The process is mathematically quite complex, but here's a short summary.

Everything starts with observations, in particular with measurements of the position of an asteroid in the sky, what we call "astrometry". Discovery telescopes extract this information from their discovery images, and make it available to everybody.

These datapoints are then used to calculate possible trajectories ("orbits") that pass through them. At first, with very few points, many orbits will be possible.

Using these orbits we can extrapolate where the asteroid will be located during the following nights, use a telescope to observe that part of the sky, and locate the object again.

From these new observations we can extract new "astrometry", add it to the orbit determination, and see that now only some of the possible orbits will be compatible with the new data. As a result, we now know the trajectory better than before, because a few of the possible orbits are not confirmed by the new data.

The cycle can then continue, with new predictions, new observations, and a more accurate determination of the object's orbit, until it can be determined with an extremely high level of accuracy.


abunchofsquirrels5 karma

Have any of you read Lucifer's Hammer by Larry Niven? In your opinion, how realistic is his depiction of an asteroid strike on Earth?

ESA_Asteroid_Day7 karma

DVK: I have – but really long ago, so I don’t remember the details. But I do remember that I really liked to book, and I remember I always wanted to have a Hot Fudge Sundae when reading it.

longdonglos4 karma

What are your thoughts on asteroid mining as portrayed in sci-fi movies? Is it feasible? If so would governments or private space programs be the first to do so?What type of minerals can be found on asteroids that would merit the costs of extraction?

ESA_Asteroid_Day8 karma

Certainly there is valuable stuff you can find on asteroids. For example, the likely easiest material you can harvest from an asteroid would be volatiles such as H2O. Then you have industrial metals, things like Iron, Nickel, and Platinum group metals. Going further, you can break apart many of the oxide minerals you would find to get oxygen (getting you closer to producing rocket fuel in-situ!). Its feasible, but still needs alot of testing both here on Earth and eventually needs to be tested on a target. It may be that governments, via agencies like ESA or NASA, may do it first, to prove the principles somewhat, but I know many commercial entities are also aggresively working towards space mining. To show you that its definitely possible, I'd like to plug the work of colleagues who have processed lunar regolith (which is similar to what you may find on asteroids) to extract both oxygen and metals. Check it out here:

  • AC

HHS20194 karma

It seems like doing this well would require international cooperation, particularly with Russia. Have you ever reached out to Russia in your work? Do you have a counterpart organization there that has a similar mission?

ESA_Asteroid_Day3 karma

DVK: Indeed international cooperation is important - asteroids don't know about our borders! We work with a Russian team to perform follow-up observations of recently discovered NEOs. Russia is also involved in the UN-endorsed working groups that we have, IAWN and SMPAG (explained in another answer).

1llm1nt14 karma

I was thinking about the asteroid threat as a teen and came up with this ideas (Hint: they are not equally serious, the level of craziness goes up real quick). Could you please comment on their feasibility?

  1. Attaching a rocket engine to an asteroid to make it gradually change trajectory, do that long in advance and it will miss Earth by thousands of km

  2. Transporting acid onto asteroid (which are mainly metal), attaching a dome-shaped reaction chamber to it, using heat and pressure to then carry out the chemical reaction to desintegrate asteroids

  3. This one is even more terrible than a previous one and totally Den Brown inspired — transporting antimatter on asteroid, impacting and causing annihilation.

Thank you for this AMA and your time!

ESA_Asteroid_Day3 karma

DVK: Well the first one is not so crazy, I have seen it presented... the difficulty is that all asteroids are rotating in one way or another. So if you continuously fire the engine it would not really help. You'd need to switch the engine on and off. Very complex. And landing on an asteroid is challenging too. Just using the 'kinetic impactor' which we will test with DART/Hera (described elsewhere in this chat) is simpler. Another seriously proposed concept is to put a spacecraft next to an asteroid and use an ion engine (like we have on our Mercury mission BepiColombo) to 'push' the asteroid away.

As for 2 and 3 I think I will not live to see that happening ;-)

Peekachooed3 karma

As a layperson, I still think using nuclear weapons against asteroids is the coolest method despite better methods generally being available.

Do you still consider the nuclear option the cool option, or has your expertise in the field combined with the real-life impracticalities made it into a laughable/silly/cliche option?

ESA_Asteroid_Day4 karma

DVK: We indeed still study the nuclear option. There are legal aspects though, the ‘outer space treaty’ forbids nuclear explosions in space. But for a large object or one we discover very late it could be useful. That’s why we have to focus on discovering all the objects out there as early as possible – then we have time enough to use more conventional deflection methods, like the kinetic impactor (the DART/Hera scenario).

Weird-Thread3 karma

What are some asteroids that are on your "watchlist"?

ESA_Asteroid_Day5 karma

We have exactly that list on our web portal:

It's called "risk list", and it includes all known asteroids for which we cannot exclude a possible impact over the next century. It is updated every day to include newly discovered asteroids, and remove those that have been excluded as possible impactors thanks to new observations.


Weird-Thread4 karma

That's quite a list! !

Do you guys ever feel stressed or afraid when you have to add another dangerous candidate (and by dangerous I mean those above 200m) is added to this Risk List?

ESA_Asteroid_Day9 karma

Yes, when new dangerous ones are added it's important that we immediately do our best to gather more data on them, observing them with telescopes in order to get the information we need to improve our knowledge of their orbit.

And then the satisfaction of getting the data needed to remove one from the list is even greater!


ruthie1473 karma

how much can experts tell from a video of a fireball or meteor? Can you work out what it's made of and where it came from?

ESA_Asteroid_Day3 karma

If multiple videos or pictures, taken from different locations, are available, then it's possible to reconstruct the trajectory, and extrapolate where the object came from.

Regarding the composition, it's a bit more difficult if nothing survives to the ground, but some information can be obtained indirectly from the fireball's color, or its fragmentation behavior. If a spectral analysis of the light can be made, it's then possible to infer the chemical composition in much greater detail.


perry_the_platypus743 karma

I've always wanted to know what the best meteorite buying site is and what their average price is??

ESA_Asteroid_Day3 karma

DVK: Serious dealers will be registered with the 'International Meteorite Collectors Association (IMCA)' - They should provide a 'certificate of authenticity' where it says that they are member there. If you are in doubt, you can contact the association and check. Normally there are rough prices for different meteorite types per gram. Rare meteorites will of course be much more expensive than more common ones. Check the IMCA web page to find a dealer close to you.

Redshirt23233 karma

What inspired you to go into this field of study?

ESA_Asteroid_Day6 karma

DVK: I started observing meteors when I was 14, just by going outside and looking at the night sky. Since then, small bodies in the solar system were always my passion.

ESA_Asteroid_Day6 karma

I was fascinated by astronomy in general since I was a kid, but the actual "trigger" that sparked my interest in NEOs was a wonderful summer course on asteroids organized by a local amateur astronomers association. I immediately decided that I would do my best to turn this passion into my job, and I'm so happy to have been able to make that dream come true.


AliceTrippDaGain2 karma

Have you played the Earth Defence Force games and if you have, which one is your favourite?

ESA_Asteroid_Day3 karma

No I have not played the Earth Defence Force games, but I just looked it up and I think I would liked it. Which one would you recommend?


Persimmon-Dismal2 karma

What is the likelihood of an asteroid hitting the Earth In the next 200 years?

ESA_Asteroid_Day3 karma

It depends on the size, large ones are rare, while small ones are much more common. You can check this infographics to get the numbers for each size class:


Ryanthequietboy2 karma

What kind of career path does it take to work in the asteroid hunting field?

ESA_Asteroid_Day2 karma

It's probably different for each of us, but here's a short summary of my own path.

I became interested in asteroids, and near-Earth objects in particular, thanks to a wonderful summer course organized by a local amateur astronomers association. Amateur astronomers play a great role in introducing people, and young kids in particular, to these topics.

Then I took physics as my undergrad degree (in Italy), followed by a Ph.D. in astronomy in the US (Hawaii in particular, a great place for astronomers thanks to the exceptional telescopes hosted there).

After finishing the Ph.D. I started my current job at ESA's NEO Coordination Centre, which allowed me to realize my dream of working in this field.


ValidatingUsername2 karma

Just read through Aidans link to the basaltic rock being used as a printing material for lunar habitation.

There is a company called Roxul that does stone woven insulation that may be able to shed some light on the research they have done to minimize their similarity to asbestos as potentially carcinogenic materials deemed safe for use in commercial and residential applications.

As the interior surfaces will essentially be 3D printed lunar regolith what are the current plans to coat or dampen the affinity for the structure to essentially be death traps for respiratory illness?

ESA_Asteroid_Day4 karma

At least initially, many of these 3d printed regolith structures would not be facing into pressurised sections, but would rather be elements placed outside and around our pressure vessels. Such structures would be things like radiation shields, landing pads or roadways, etc. In the future, if we move towards forming hermetically sealed structures, then your point is a good one. Looking into terrestrial solutions to this problem would be a great start! - AC

GayFrogChild1 karma

How can I join you when I'm older?

ESA_Asteroid_Day2 karma

DVK: Somebody was asking about our career paths... Study aerospace engineering or math or physics or computer science, get a Masters. Possibly a Ph.D. Then apply for my position when I retire. Check here for how to apply at ESA:

n815e0 karma

How much is too much?

ESA_Asteroid_Day2 karma

DVK: 42 again