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[Table] Asteroid Day AMA – We’re engineers and scientists working on a mission that could, one day, help save humankind from asteroid extinction. Ask us anything!

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There are several people answering: Paolo Martino is PM, Marco Micheli is MM, Heli Greus is HG, Detlef Koschny is DVK, and Aidan Cowley is AC.
Questions Answers
Can we really detect any asteroids in space with accuracy and do we have any real means of destroying it? 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.
MM
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? 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.
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? 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.
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Why are you quite convinced that you know all object of that size? And what is your approach in finding new celestial bodies? 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: https://www.esa.int/ESA_Multimedia/Images/2018/06/Asteroid_danger_explained
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 https://www.esa.int/ESA_Multimedia/Images/2017/02/Flyeye_telescope.
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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 DVK: Indeed, that's cool. Maybe you can go and visit it one day.
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What about Interstellar objects however, like Oumuamua? 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.
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? DVK: We do not keep things secret – all our info is at the web page http://neo.ssa.esa.int. 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.
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? 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!
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So you’re saying it was discussed and shelved? 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: https://www.cosmos.esa.int/documents/336356/336472/PDC_2019_Summary_Report_FINAL_FINAL.pdf/341b9451-0ce8-f338-5d68-714a0aada29b?t=1569333739470
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.
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? 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.
MM
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How often do impacts from that direction happen, compared to impacts from visible trajectories? 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.
MM
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? 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.
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? DVK: There are programmes that monitor the Moon and look for flashes from impacting small asteroids (or meteoroids) - https://neliota.astro.noa.g 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.
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? DVK: There are international entities in place, mandated by the UN: The International Asteroid Warning Network (http://www.iawn.net) and the Space Mission Planning Advisory Group (http://www.smpag.net). 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.
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There is no actual risk of any sizable asteroids hitting earth in the foreseeable future. Any preparation for it would just be a waste of money. DVK: Indeed, as mentioned earlier, we do not expect a large object to hit is in the near future. We are mainly worried about those in the size range of 20 m to 40 m, which happen on average every few tens of years to hundreds of years. And where we only know a percent of them or even less.
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? 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.
this is another reply 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
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? 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
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? 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.
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Why is there less probability of larger asteroids hitting earth? DVK: There are less large objects out there. The smaller they are, the more there are.
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Is there any chance that your experiment will backfire and send the asteroid towards earth? PM: Not at all, or we would not do that :) Actually Dimorphos (the Didymos "moon") will not even leave its orbit around Didymos. It will just slightly change its speed.
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? 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.
HG
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So then would it be easier to train oil drillers to become astronauts, or to train astronauts to be oil drillers? 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.
HG
If budget was no object, which asteroid would you most like to send a mission to? 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 (https://en.wikipedia.org/wiki/25143_Itokawa), which was visited by Hayabusa spacecraft. So we already have some solid prospecting carried out for this 'roid! - AC
this is another reply Not sure if it counts as an asteroid, but Detlef and myself would probably choose ʻOumuamua, the first discovered interstellar object.
MM
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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. 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.
https://www.esa.int/Science_Exploration/Space_Science/ESA_s_new_mission_to_intercept_a_comet
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 proves beneficial. While it is probably quite problematic to land the payload, it could save fuel or am I mistaken? Neat idea! Wonder if anyone has done the maths on the amount of fuel you would need/save vs certain targets. - AC
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..
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? 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.
How much are we prepared against asteroid impacts at this moment? 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.
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? Here’s our recently updated infographics with the fraction of undiscovered NEOs for each size range: https://www.esa.int/ESA_Multimedia/Images/2018/06/Asteroid_danger_explained
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.
MM
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DVK: And to add what MM said - Check out http://neo.ssa.esa.int. There is a ‘discovery statistics’ section which provides some of the info you asked about. NASA is providing similar information here https://cneos.jpl.nasa.gov/stats/. 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: http://www.minorplanetcenter.org, ‘observers’, ‘sky coverage’. That is a tool we use to plan where we look with our telescopes, so it is a more technical page.
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. 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": http://neo.ssa.esa.int/risk-page
It is automatically updated every day once new observational data is processed.
MM
What are your favourite sci-fi series? 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’.
this is another reply Big fan of The Expanse at the moment. Nice, hard sci-fi that has a good impression of being grounded in reality - AC
this is another reply 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'.
HG
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. 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.
MM
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? 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: http://www.esa.int/ESA_Multimedia/Images/2019/10/Oxygen_and_metal_from_lunar_regolith
AC
Will 2020's climax be a really big rock? DVK: Let's hope not...
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? 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.
MM
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Is this to say that it was within specific solid angles for the entire time that we could have observed it given its size and speed? Yes, precisely that. We got unlucky in this case.
MM
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? DVK: I have – but really long ago, so I don’t remember the details. But I do remember that I really liked the book, and I remember I always wanted to have a Hot Fudge Sundae when reading it.
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 disintegrate asteroids 3. This one is even more terrible than a previous one and totally Dan Brown inspired — transporting antimatter on asteroid, impacting and causing annihilation. Thank you for this AMA and your time! 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 ;-)
What is the process to determine the orbit of a newly discovered asteroid? 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.
MM
What are some asteroids that are on your "watchlist"? We have exactly that list on our web portal: http://neo.ssa.esa.int/risk-page
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.
MM
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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? 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!
MM
What inspired you to go into this field of study? 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.
MM
this is another reply 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.
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? 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).
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? 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).
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? https://www.reddit.com/space/comments/hdf3xe/footage_of_a_meteor_at_barrow_island_australia/?utm_source=share&utm_medium=web2x 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.
MM
I've always wanted to know what the best meteorite buying site is and what their average price is?? DVK: Serious dealers will be registered with the 'International Meteorite Collectors Association (IMCA)' - https://www.imca.cc/. 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.
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? 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
What kind of career path does it take to work in the asteroid hunting field? 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.
MM
this is another reply DVK: Almost all of us have a Master's degree either in aerospace engineering, mathematics, physics/astronomy/planetary science, or computer science. Some of us - as MM - have a Ph.D. too. But that's not really a requirement. This is true for our team at ESA, but also for other teams in other countries.
What is the likelihood of an asteroid hitting the Earth In the next 200 years? 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: https://www.esa.int/ESA_Multimedia/Images/2018/06/Asteroid_danger_explained
MM
Have you played the Earth Defence Force games and if you have, which one is your favourite? 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?
HG
How close is too close to earth? Space is a SUPER vast void so is 1,000,000 miles close, 10,000,000? And if an asteroid is big enough can it throw earth off its orbit? DVK: Too close for my taste is when we compute an impact probability > 0 for the object. That means the flyby distance is zero :-) Those are the objects on our risk page http://neo.ssa.esa.int/risk-page.
If an object can alter the orbit of another one, we would call it planet. So unless we have a rogue planet coming from another solar system (verrry unlikely) we are safe from that.
How can I join you when I'm older? 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: https://www.esa.int/About_Us/Careers_at_ESA/Frequently_asked_questions2#HR1
How much is too much? DVK: 42 again
Are you aware of any asteroids that are theoretically within our reach, or will be within our reach at some point, that are carrying a large quantity of shungite? If you're not aware, shungite is like a 2 billion year old like, rock stone that protects against frequencies and unwanted frequencies that may be traveling in the air. I bought a whole bunch of the stuff. Put them around the la casa. Little pyramids, stuff like that. DVK: If I remember my geology properly, Shungite forms in water sedimental deposits. This requires liquid water, i.e. a larger planet. So I don't think there is a high chance to see that on asteroids.
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[Table] IAmA: We are experts of the European Space Agency ESA working on Near Earth Objects such as asteroids, their detection and deflection and the respective activities like ESA’s proposed Asteroid Impact Mission (AIM) – ask us anything!

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Date: 2016-06-30
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Questions Answers
Can we call asteroids rocks? Why?? And does the theory that explains how earth water came from asteroids still available and working? Also do you think it is worthy to spend a lot of the space agencies's budget to explore an asteroid? [CB] Whether asteroids can be considered as rocks is a good point! In fact, that's one of the main things we want to send AIM and DART to Didymos to find out. At the moment it is not entirely clear whether they are really solid in nature, like a lump of granite, or more like aggregated smaller rocks. Scientific simulations seem to suggest the latter since it seems likely that the binary Didymos system formed by a single larger asteroid losing material to form the secondary one. The low-frequency radar on the MASCOT-2 lander will send radio waves through the smaller asteroid so that we will be able to determine the internal structure. However, we do not believe that there is any water on or in the asteroids. Comets consist largely of water ice and one the objectives of ESA's Rosetta mission was to check whether the isotopes of that water matched that in our oceans. In fact, the answer to that question was negative, so it does not look as though our ocean water came from comets.
As far as whether it is worth spending money on doing this, well, firstly I would have to say that AIM is a relatively cheap mission. Secondly, expanding our scientific knowledge of the universe is something that it is very difficult to put a price on. In addition, the AIM mission is a technology demonstrator with an optical downlink, deployable cubesats with intersatellite-link capability two types of planetary radar, optical sensors etc. Much of this kind of technology would be needed for a potential human mission to Mars, say. Finally, if we do work out what asteroids are made of and what happens when we hit one with a projectile, this will definitely help us in the future should we need to deflect one away from Earth in the future.
Asteroids contain lots of different materials. Certainly lots of metals and metal compounds, as well as silicates and organic matter. So calling them "rocks" isn't wrong.
Water ice and other volatile material is probably very rare on asteroids, certainly on asteroids whose orbits are close to the Earth orbit, because these will have been "baked out" over the millennia.
There is however an enormous amount of water ice, carbon dioxide ice and carbon monoxide ice and other volatile on comets. Comets are on quite different orbits than most asteroids, but there is a kind of grey area. Some objects that look like asteroids may in fact be comets, or "old comets" that have fizzled out, so to speak.
Investigating asteroids certainly is a worthwhile endeavour. Much of the material there is still very pristine, despite the baking out and the exposure to harsh radiation. We simply cannot find such material on Earth. It would have eroded or been destroyed or changed long ago. We need to go out there and find it if we want to learn about what made up the Earth as it formed out of gas and dust, 4.6 billion years ago.
What kind of systems do we currently have to deflect asteroids coming our way? We have many ideas on how a deflection system would look like. Clearly the final choice would depend on the kind of threat, in particular the collision epoch and the asteroid size.
Hi guys! Two questions: how much information about an asteroid are you able to get from the ground/satellites without sending a probe out? Other than size,rotation, albedo,etc. [BGG] Indeed from ground you can get size and shape, rotation speed and axis orientation, and some albedo reflectivity properties, but also by using spectrometry the composition of their surface. In case of binary asteroids, such as Didymos (Asteroid Impact Mission's targeted asteroid), you can also get their mass from the time it takes to rotate around each other... a so their density. Using satellites, on top of increasing accuracy and certainty on the measures, it is possible to study the sub-surface and deep interior using high and low frequency radars respectively. (PC) Ground observations are based mostly on optical observations, the so called spectrometry gives hints on the external compositions and the so called astrometry gives information on the positions. This is sufficient to define the type of asteroid. Curves of lights can be used, and in some rare cases also radar measurements, can gives information on the shape and spin axes. But all the research done on top of the basic position knowledge is limited to large sized objects due to the limited amount of light reflected and received on Earth. (artificial) Satellite being way closer to the object under study can provide more accurate information also for minor objects and can also carry instruments that sounds the interior of the structure (radar), measures the magnetic fields, makes a thermal model and perform experiments to precisely determine the mass of the object, increasing further the knowledge of the inner structure. Satellites can even carry, as Rosetta did with Phileae and proposed AIM with MASCOR2, landers that perform in-situ science, impossible from Earth.
U/ESAAsteroidDayAmA Why? :) (VP) Paolo is an amateur astronomer and he's got that asteroid named after him! See kids? Learn your science and you can get your own asteroid!
How do you detect the path of an asteroid and if it were to be projected at Earth what must we do to brace for an impact? None of the thousands if Earth crossing asteroids currently known pose a concrete impact risk. But the problem is that we don't know even close to all of the Earth crossing asteroids that are big enough t cause massive, perhaps even global damage. What needs to be done right now is to go on looking and to chart the orbit of every new body that is found. This is called a sky survey. Then we need to understand much more about their interior composition. We really do not understand these small bodies very well. The more we learn, the better our chances are of our winning out against a hazardous asteroid, should one be found. In case an asteroid was to be detected in an Earth collision course our options would depend on the advance time we have before the impact. In a likely scenario we would have some years to plan a deflection option. (PC) Usually the path is derived on the basis of optical observations of moving objects in stars fields. Background stars are used as reference of angular motion of an object and repeating such observation over time create a series of angular positions with respect to Earth. Software simulations are run to find an orbit compatible with such series of angular positions and as a result we understand the absolute position (including distance from Earth). Further observations, sometimes over a time span of months, will help in reducing the uncertainty of orbit propagation. This means that we can predict with higher accuracy where the object will be at some point in future. The level of accuracy in our propagation give us the confidence for an actual impact and if so... this is what we are discussing all day today.
What's the usual size of Asteroids coming our way? [CR] Great question! I will start with the first question: Q: What's the usual size of Asteroids coming our way? A: There is an excellent reference with title “The population of near-Earth asteroids” by Harris and D’Abramo you can find here] ([Link to www.sciencedirect.com In there, Figure 4 shows the relationship of how many NEOs are there of a given size. Basically, there are asteroids in sizes varying from sand corn sized to many kilometres in diameters. The rule of thumb is that there are many more small sized asteroids and fewer bigger ones. The relationship actually follows a power law. This is demonstrated by the fact that you can look up in the night sky and see harmless shooting stars that are caused by very small asteroids (small particles) and that big asteroids impacts are not part of our every day experience. Sorry if the reference is behind a pay wall but you might be able to find the source if you do some smart googling….I will try to find it free in the meantime as well.
[CR] Answer to question three: Q: What's the size from which we should be starting to get worried? A: The Chelyabinsk asteroid that injured about 1500 people (no one died) in February 2013 was around 20 m in diameter so anything in that size regime can be cause for concern. Smaller asteroids will only cause very localized damage (such as in Chelyabinsk) and here of course the impact location would matter. The same asteroid coming in over an ocean would not cause any harm, for instance. On the other hand, asteroids that are few kilometres in diameter could have global consequences such as what likely happened to the dinosaurs.
Link to en.wikipedia.org
How often does an object cross the earth's orbit at a time when it threatens to impact the moon more than the earth? Has deflection of these objects been considered, too? The Moon is a much smaller body with respect to Earth. Asteroid impacts on the moon are therefore extremely rare and as we struggle to compute impact risks for the Earth, the ones for the Moon would be subject to even larger uncertainties.
That I know of, the scenario you envisage has not been seriously considered so far (for the reasons explained above)
(SB) Lunar asteroid impacts are seen periodically from Earth:, eg Link to www.space.com As for deflection, there are plenty of craters already on the Moon, another one would not make much difference...
Once we have determined the orbit of an asteroid through space, which requires observing it repeatedly at different times, we can start predicting its future orbit. This is called numerical propagation, which is a big word for using a computer to compute how all kinds of perturbations are going to be changing the orbit of the asteroid at any later point in time.
Such perturbations may be caused by the gravity of the Earth, the Moon and other bodies, but also by the small but constant pressure exerted by sunlight, or by the heat which is radiated off a\an asteroid surface. With time, even small things make a difference.
If the threat of an impact and the effectiveness of a deflection are considered (the latter luckily has not been necessary so far, but one day, it will be). this numerical propagation is vital, so we have to get it right!
(PC) on top of already provided answers... have in mind that there is no atmosphere protecting the moon surface from small-size objects, therefore so many sign of impacts there.
Not to mention no erosive processes of any kind!
Last updated: 2016-07-01 08:38 UTC | Next update: 2016-07-01 08:48 UTC
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@article{osti_22525423, title = {RADIO ASTROMETRY OF THE CLOSE ACTIVE BINARY HR 5110}, author = {Abbuhl, E. and Mutel, R. L. and Lynch, C. and Güedel, M.}, abstractNote = {The close active binary HR 5110 was observed at six epochs over 26 days using a global very long baseline interferometry array at 15.4 GHz. We used phase referencing to determine the position of the radio centroid at each ... This system was first detected as binary by astrometry and the white dwarf was not visually detected until 1862. Examples of visual binaries in the southern skies resolvable through small telescopes include α Crucis, β Crucis and γ Cen and Castor in Gemini. Some stars appear close together when viewed through a telescope but in fact are not gravitationally bound and can be hundreds of ... DTIC ADA486312: Adaptive Optics Photometry and Astrometry of Binary Stars. III. A Faint Companion Search of O-Star Systems Item Preview build-index: given a FITS binary table with RA,Dec, build an index file. This is the “easy”, recent way. The old way uses the rest of these programs: usnobtofits, tycho2tofits, nomadtofits, 2masstofits: convert catalogs into FITS binary tables. build-an-catalog: convert input catalogs into a standard FITS binary table format. Automatic saving of selected options and files. Can create master files for dark and flat & flat-darks to reduce processing time. Limited memory use, independent of the number of images stacked. Bayer algorithm for DSLR/OSC cameras; For stacking the internal routine compares the image star positions to align. To uncheck/untick poor images there is an option to do that automatically. First ... Some binary motion is not easily approximated by parallactic motion – in the first example in Fig. 2, a binary period of just under half a year gives a smooth well-behaved curve, but one impossible to fit well with a single-body astrometric fit. The third example is one of a small but significant minority in which binary motion at a period close to 1 yr enlarges (or in other cases contracts ... For those that aren’t, here are a few options for converting to FITS BINTABLE (binary table) format: * text2fits.py in the Astrometry.net package—useful for CSV (comma-separated values) and other ASCII text inputs; this is a simple parser and takes a huge amount of memory to process big files. It would be possible to make it “stream” the inputs and outputs, but I haven’t done that ... By calculating the optical depth due to the mentioned stellar populations, the numbers of the binary astrometric microlensing events being observed with Gaia with detectable binary signatures, for the binary fraction of about 0.1, are estimated to be 6, 11, 77, and 1316, respectively. Consequently, Gaia can potentially specify the binary fractions of these massive stellar populations. However ... Astrometry using very long baseline interferometry (VLBI) can be employed to provide these model-independent distances with very high precision via the detection of annual geometric parallax. Using the Very Long Baseline Array, we have observed two binary MSPs, PSR J1022+1001 and J2145–0750, over a two-year period and measured their distances to be pc and pc respectively. We use the well ... This binary was first detected by the Hipparcos satellite. The astrometry is almost identical to that of the original detection. While the proper motion is quite low (0.11 arcsec yr −1; van Leeuwen 2007), the almost identical astrometry leads us to conclude that the companion has common proper motion with the primary. HD 212097 (WDS 22213+2820).

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