NASA has a plan defend the Earth from asteroids

The trick is spotting the near-Earth objects first, according to NASA researchers presenting at the 2019 American Physical Society April meeting in Denver

WASHINGTON, D.C., April 16, 2019 — A mere 17-20 meters across, the Chelyabinsk meteor caused extensive ground damage and numerous injuries when it exploded on impact with Earth’s atmosphere in February 2013.

Chelyabinsk Meteor

To prevent another such impact, Amy Mainzer and colleagues use a simple yet ingenious way to spot these tiny near-Earth objects (NEOs) as they hurtle toward the planet. She is the principal investigator of NASA’s asteroid hunting mission at the Jet Propulsion Laboratory in Pasadena, California, and will outline the work of NASA’s Planetary Defense Coordination Office this week at the American Physical Society April Meeting in Denver — including her team’s NEO recognition method and how it will aid the efforts to prevent future Earth impacts.

“If we find an object only a few days from impact, it greatly limits our choices, so in our search efforts we’ve focused on finding NEOs when they are further away from Earth, providing the maximum amount of time and opening up a wider range of mitigation possibilities,” Mainzer said.

But it’s a difficult task — like spotting a lump of coal in the night’s sky, Mainzer explained. “NEOs are intrinsically faint because they are mostly really small and far away from us in space,” she said. “Add to this the fact that some of them are as dark as printer toner, and trying to spot them against the black of space is very hard.”

Instead of using visible light to spot incoming objects, Mainzer’s team at JPL/Caltech has leveraged a characteristic signature of NEOs — their heat. Asteroids and comets are warmed by the sun and so glow brightly at thermal wavelengths (infrared), making them easier to spot with the Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) telescope.

“With the NEOWISE mission we can spot objects regardless of their surface color, and use it to measure their sizes and other surface properties,” Mainzer said.

Discovering NEO surface properties provides Mainzer and her colleagues an insight into how big the objects are and what they are made of, both critical details in mounting a defensive strategy against an Earth-threatening NEO.

For instance, one defensive strategy is to physically “nudge” an NEO away from an Earth impact trajectory. But to calculate the energy required for that nudge, details of NEO mass, and therefore size and composition, are necessary.


The NEOWISE space telescope spotted Comet C/2013 US10 Catalina speeding by Earth on August 28, 2015. This comet swung in from the Oort Cloud, the shell of cold, frozen material that surrounds the Sun in the most distant part of the solar system far beyond the orbit of Neptune. NEOWISE captured the comet as it fizzed with activity caused by the Sun’s heat. On November 15, 2015, the comet made its closest approach to the Sun, dipping inside the Earth’s orbit; it is possible that this is the first time this ancient comet has ever been this close to the Sun. NEOWISE observed the comet in two heat-sensitive infrared wavelengths, 3.4 and 4.6 microns, which are color-coded as cyan and red in this image. NEOWISE detected this comet a number of times in 2014 and 2015; five of the exposures are shown here in a combined image depicting the comet’s motion across the sky. The copious quantities of gas and dust spewed by the comet appear red in this image because they are very cold, much colder than the background stars. CREDIT NASA

Astronomers also think that examining the composition of asteroids will help to understand how the solar system was formed.

“These objects are intrinsically interesting because some are thought to be as old as the original material that made up the solar system,” Mainzer said. “One of the things that we have been finding is that NEOs are pretty diverse in composition.”

Mainzer is now keen to leverage advances in camera technology to aid in the search for NEOs. “We are proposing to NASA a new telescope, the Near-Earth Object Camera (NEOCam), to do a much more comprehensive job of mapping asteroid locations and measuring their sizes,” Mainzer said.

NASA is not the only space agency trying to understand NEOs. For instance, the Japan Aerospace Exploration Agency’s (JAXA’s) Hayabusa 2’s mission plans to collect samples from an asteroid. And in her presentation Mainzer will explain how NASA works with the global space community in an international effort to defend the planet from NEO impact.

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The presentation, “NASA’s Planetary Defense Coordination Office at NASA HQ,” took place at 10:45 a.m. MT, Tuesday, April 16, in room Governor’s Square 14 of the Sheraton Denver Downtown Hotel. ABSTRACT: http://meetings.aps.org/Meeting/APR19/Session/X05.1

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73 thoughts on “NASA has a plan defend the Earth from asteroids

  1. Much more concerned about asteroid or comet impact than a little beneficial warming and extra plant food.

    • Karl Valentin explained Liesl Karlstadt he would look for an accommodation in a coal mine. Because of the comets.

      Liesl Karlstadt: “but comets are so rare!”

      Karl Valentin: “Safety is more important than rarity!”

  2. Imagine to witness that rock fall 66 million years ago, the wave it must have made, that traveled far inland, EEEK!

  3. Aye, THERE’S the rub; seeing them BEFORE they are glowing streaks in the skies. For that, we’re going to need better, and probably space-based telescopes. Of which precisely ZERO are in the design phase, or even proposed.

    • The James Webb Space Telescope (JWST) will have a mid-infrared imager, primarily for studying cosmological phenomena such as red-shift. It will also be used for observing comets and Kuiper belt objects. Presumably, it could (in its spare time) spot NEOs.

      The first study contracts for JWST were let in 1997, and the launch date goal was 2007. The current launch date goal is March of 2021, and from what I read of some of the difficulties they’re having, it may slip even more. It is truly a “Generation Spacecraft” in that it will have taken a generation to go from concept to flight….

      Whenever I read a headline that includes “NASA has a plan” I know that it’s for something that won’t happen in my lifetime.

      • At one time, a President said “We will go to the Moon in this decade”, and NASA did it! Of course, those days are long gone.

  4. Maybe they can detect small objects with temperature above absolute zero in space and maybe they can’t in any meaningful way. Detection in the Thermal IR bands, 4 to 14 um, is done mostly by rare earth oxide crystals, like Yb (ytturbium) and they are notoriously slow to saturate, read, discharge, and re-saturate. This means that the detection size is limited. I’m sure NASA has sensors way beyond my experience, but meaningful detection of an object traveling 14,000 mph, only somewhat above absolute zero, and only 20 meters across? Hard to believe. If we had enough warning lead-time to kiss our ass goodbye I would be surprised.

    • NEOWISE is a space based telescope. It works in the 3.4 and 4.6 um bands using HgCdTe detectors.

      Only initial detection is done by NEOWISE. Follow-up observations to determine orbit is by gound-based telescopes on optical wavelengths. Most of the detected objects have been in the 0.2-2 km diameter range, the biggest as large a 8.5 km (not far short of the Chicxulub impactor!) and the smallest about 0.1 km.

  5. The ‘giving the NEO a nudge’ phase is going to be even more of a challenge than detecting the NEO.

    Fortunately, while NEOs weighing 15m across are common, those that that actually strike the earth are pretty uncommon; in fact, the Chelyabinsk event (which did not actually result in a ‘strike’) was the biggest event in over a hundred years.

      • one due today 18th at .6 LD listed at spaceweather
        not sure how close it needs be to get dragged into our atmosphere/gravity

    • If they are planning any sort of physical contact to ‘nudge’ NEOs away from Earth, they had better well know the composition of the object as well as CG and moments. Absent this data they could very well be making the situation worse. A thermal signature is hardly enough data to determine any of this. Radar won’t do it either. Each will tell you something, but those ‘somethings’ can also be produced by a myriad of diverse objects. Chaff clouds look like solid aircraft, and will heat up as well, but they are notoriously hard to nudge. I suppose in theory we could assess the mass of such a conglomeration if we could measure course deviations caused by gravitational fields, but are our measurement capabilities precise enough on small objects of unknown mass or composition to make this assessment with any confidence?

      This isn’t completely true, but I suppose they had to dumb it down for the audience: “With the NEOWISE mission we can spot objects regardless of their surface color, and use it to measure their sizes and other surface properties,”

      I would posit that its surface color will have a very big effect on the amount of solar heating the object receives. It may make ‘black bodies’ easier to see.

      • If you do your nudging when the NEO is far enough away, it’s like spoiling the aim of a sniper. The exact effect of the nudge doesn’t really matter much, as long as it changes the trajectory. Any change will make it miss.

          • All objects fall together in a gravitational field. This led Einstein to the General Theory of Relativity and the “Equivalence Principal” where a gravitational field is equivalent to an accelerated coordinate frame, hence everything in the same field moves together. This led to the the the geometric interpretation of gravity as curvature in space-time.

          • Obviously, but perhaps I should have elaborated my previous response. The purpose of detecting these objects is to be able to prevent those on a collision course with earth from exterminating life. The mass of the object will be intrinsic in the calculation of the course changing force to be applied, whether it be laser, ion propulsion, nuclear explosion, white paint or one of the even more esoteric proposals. My fault for not using enough words, not something I am usually guilty of.

  6. I’m not serious about this. But the same technology used to locate small dark asteroids near the Earth would also probably detect any UFO’s in near space that were watching us. If the government said they were going to spend say 25 million dollars to look for UFOs there would be consequences. But if they say they are going to spend the same money to look for asteroids to “defend the planet” (where’s Superman when you really need him?) it’s all OK. I don’t object to the government looking for asteroids. I mean somebody ought to take a look even if they find nothing.

  7. To prevent another such impact, Amy Mainzer and colleagues use a simple yet ingenious way to spot these tiny near-Earth objects (NEOs) as they hurtle toward the planet.

    Spot ≠ prevent

    Granted, prevention is impossible unless NEO’s can be spotted sufficiently far in advance of impact… But, unless they intend to start practicing on intercepting and neutralizing NEO’s not currently on an Earth-bound trajectory, spotting them will have limited value.

    • Some might appreciate the ability to use the warning time for a BIG impactor—however short—to bend over, grab their ankles and . . .

    • Oh no, I’m sure that they will have that covered. They can create a model, call it the asteroid strike simulation with impact prediction estimate (ASSWIPE).

      All they need to do is program it to predict that the asteroid will miss the earth, and voila, problem solved.

      Garbage in – Gospel out, just like the climate models

    • Because of thrusts due to outgassing near the sun we will have very short reaction times of only a few weeks. This is a mission requiring nuclear powered rockets prepositioned in low earth orbit.

    • Except for elephants, hippos, rhinos, horses, moose, whale, large dogs, lions tigers & bears and all the other mammals weighing over 100 lbs that survived the Late Quaternary extinction, mostly because people didn’t eat them.

      • Yeah, the North American Lions , Bears, Giant sloths etc did not survive , and their African cousins did , because of African humans distaste for pachyderm quarter pounders, or perhaps the African’s lacked the hunting prowess of the North Americans . I refer you to “The Cosmic Tusk ” , look up “The Burn paper ” , evidence found in hundreds of sites throughout the Globe for a massive burn during the YD epoch , and just below it, evidence that the cause was most likely either a comet/ asteroid or an extremely powerful CME . For some reason,what is now sub-Sahara , lacks the black mat and impact proxies . Perhaps that is why nowhere else but Africa did the Mega Fauna survive . Also of interest is Anthony Peratt’s(World renown Plasma Physicist of Los Alamos lab) study of petroglyphs. See Youtube for a one hour tour. Cheers!!!.

    • And only 3700 years ago, an air burst bolide exploded over an ancient civilization a little north of the Dead Sea, wiping out this civilization. The scorching of the rocks and pottery shards indicate that the explosive force may have been equivalent of a 10 megaton nuclear explosion. The soil was so badly baked that the area didn’t start to recover for almost 700 years.

      You may have read of the place; a little city called Sodom.

      https://www.universetoday.com/140752/a-meteor-may-have-exploded-in-the-air-3700-years-ago-obliterating-communities-near-the-dead-sea/

    • While a lot of large animals (not all mammals) died 12K years ago, the date of extinctions for each ranged over several hundred (or more) years.
      There isn’t any evidence that the deaths were caused by an impact.

  8. If the thing is big like the one that killed dinosaurs, and is heading straight for bullseye impact it will be hard to nudge it enough, unless detected very early on. I have heard of denoting nuclear bombs near asteroid to vaporize some of the surface enough to move the thing but I have no idea the energy needed.

  9. As the climate scam unravels NASA may redirect its grant seeking activities and focus on real threats such as asteroids, solar storms, orbiting debris and super volcanoes.

  10. I think the best way to deflect incoming asteriods is to use a laser beam powered by a Solar Power Satellite (SPS) to push the asteriods out of the way.

    And a laser/SPS doesn’t have to contend with matching orbits with the asteriod, and the time it takes for a vehicle to reach the asteriod, it can start deflecting the asteriod immediately after it is spotted.

    When not deflecting asteriods, the laser/SPS could be used to propel small probes at high speed to every interesting spot in the solar system in a short period of time.

    And the SPS could also be used to supply power to facilities in orbit or on the Moon and to propel vehicles back and forth between the two.

    The U.S. space program should set a goal of putting an SPS in space before the Chinese do. The Chinese are planning on having a fully fuctional SPS by the year 2030. NASA better get busy if they want to win this race! And it might not be just a race with the Chinese, but a race with Earth’s survival.

    • A major challenge with such technology is trust. Such things look an awful lot like weapons: big, badass, very powerful weapons.

      It helps that the Cold War is over, and all, but, still, would we want the Ruskies or Chinese to have such things in orbit?

      Would the Ruskies or Chinese want us to have such things in orbit? Would they believe us if we pinky-promised that we would never, ever aim those devices downward?

      • Dave Burton
        April 17, 2019 at 10:00 pm

        Yes, I agree that that perhaps could be a serious concern we should keep in mind.

        However, I think it’s just great that NASA and others are finally starting to take this threat seriously. The chances of a Chixalub-sized thing spoiling our day in our lifetime are about zero.

        I don’t particularly care if it takes a century or two to get something workable up and running but at least we are making a start. The current missions to Ryugu and Bennu can only help our understanding of these potential threats. We have already learnt a lot in the last 50 years…we’ll be so much wiser in 200 and much better prepared.

        A much better use of NASA funds than AGW nonsense.

    • Threat objects are a few kilometers in size and would be deflected by detonation of a nuclear device of a few megatons weighing a few thousand pounds. The most stressing objects driving the rocket delta velocity requirements are comets which have an icy conglomerate structure and undergo unpredictable accelerations due to outgassing when they pass close to the sun. These unpredictable delta velocities can place the comet on a collision course with the earth on the outgoing leg of the comets orbit about the sun. Thus, the warning time may be as short as 30 days or so. The velocity requirement starting from low earth orbit is about 60,000 ft/sec but the acceleration requirement is only about 1 ft/sec/sec. Given the large velocity requirement but low acceleration requirement (starting from low earth orbit) this would appear to be a good application of nuclear powered rockets. And, it is interesting to consider how the nuclear rocket power supply could be incorporated into the nuclear device payload. This mission will require not just Rocket Scientists but Nuclear Rocket Scientists!

  11. “The trick is to spot them first.” Yeah, “before they spot us” I suppose. Let’s try “The trick is, first, to spot them.” Then we’ll have more time to wring our hands and dance around in circles.

  12. Impacts from space objects is down substantially in the last 4,500,000,000 years.

    I’m not skeert. If NASA wants to look, fine. If they don’t, that’s fine, too.

      • Spending money on the grossly unlikely is wasteful.

        One in five billion . . . I like my odds.

        • You just pulled that number out of your ass. We don’t know enough about large impacts over time to be able to even compute meaningful odds. However we do know that the planet has been hit multiple times by large objects in the last 500Myrs, which is more than we can say about CO2 induced catastrophic global warming. I don’t think it would be wise to assume that another impact is “grossly unlikely” during the foreseeable future of our species. I’m not suggesting spending billions on it every year, but IMHO it would be worth a few million every budget cycle to at least identify what kind of objects are still out there that could be a risk. At least then we would have a shot at being able to calculate some reasonably accurate odds of a catastrophic event.

          • The one in 5 billion is for space debri. Easy to find on duh web.

            Chances for hit by meteor one in 700,000.

            Both gross speculation.

            ‘On the other hand, an impact by a 100-metre (328-foot) NEO, the smallest believed capable of causing regional devastation, is estimated to occur about once every 1,000 years on average. (An impact from a body the size of the Chelyabinsk meteorite of 2013 [17 metres (56 feet)] is expected to occur once per century.)’ – Britannica

            71% of the earth is ocean. Many parts of the land is sparcly populated. MOST future impacts will affect NO ONE.

            ‘The apparently only verified case of a meteorite hitting and injuring a human being occurred in 1954.’ – Brittanica

            Humans may have been directly killed at Tunguska, but none are documented.

            Worry all you want to. Please don’t spend my money on your phobia.

          • Gamecock,
            You are conflating stats. The odds of an individual being hit by a piece of space debris may indeed be 1 in 5 billion (although even that’s an educated guess), but space debris impacts the planet daily. Most of it is small enough that it burns up in the atmosphere, otherwise that stat would be much smaller. It’s the larger objects we need to be concerned about because they can cause a lot of deaths even if they don’t directly hit a single person. The problem is, we don’t have good data on the population of potentially dangerous Earth crossing objects. In order to even access the need for a defensive system, we at least need to do a better study of these objects so that we can make an informed decision. That will require some money to be spent. The amount we waste on the UN every year would more than sufficient, for example.

        • Impacts large enough to cause a major short-term climate perturbation, say only just enough to completely ruin harvests for a year or two (and thereby incidentally kill off 99% of humanity) are probably not that rare, perhaps a few hundred thousand years apart.

          • One of the challenges of developing a system to deal with events that infrequent is that no technology we build will last even a thousandth that long. In fact, in my experience, anything with complex technology is unlikely to work twenty years after it’s built. We celebrate, and congratulate the engineers if satellites function for more than a decade.

            One of the great banes of human civilization has always been the fact that knowledge passes away (1 Cor 13:8). Tapes rot, libraries burn, and vast amounts of irreplaceable data are continually being lost because of the failures of existing storage technology. Even priceless satellite data is lost, like sea ice measurements from SeaSat-1 and Nimbus-6.

            The longest-lasting long-term data storage medium we have is probably the M-Disc. It is hoped that it will last several hundred years.

            So, whatever we build, it’s at least a 10,000-to-1 longshot that it will ever prove useful.

            That doesn’t mean it isn’t worthwhile doing, but what are the chances that someone will actually build it, given such odds?

            Well, maybe not zero. The climate scare is, perhaps, evidence that it could be done, with sufficient hype, and enough special interest support.

            If mankind can build a $1.5 trillion climate industry to combat the imaginary catastrophic consequences of something which is actually, according to all objective evidence, beneficial, then perhaps it’s not too much to hope that mankind could build a defense a against meteor strikes.

          • Dave Burton,
            That’s why everything must be maintained and replaced as needed. But in order for it to be available when you need it, it must be built first. As for data, in the digital age it’s easy to copy it to new mediums when the old stuff degrades. I still have digital photographs from 20 years ago, even though the original media (floppy disk) has long expired. There’s really no reason to lose data today except for sloppiness, laziness, or lack of foresight.

          • “probably not that rare, perhaps a few hundred thousand years apart”

            The planet will be iced over more often. And I wonder your definition of ‘rare.’

            My definition:

            1. (of an event, situation, or condition) not occurring very often

            A few hundred thousand years doesn’t sound very often to me.

        • Gamecock,

          starting with the KT impact, it created a magnitude 11 and globally a 9, which energized the Deccan Traps into a massive flow: https://youtu.be/bRNA_xct5JU

          Earth has been impacted 500+ times since the Clovis comet: https://cometresearchgroup.org/comets-diamonds-mammoths/#impact-overview

          Bakken crater caused massive 600’+ Tsunami in the Indian Ocean 5,000 years ago, Sodom was friend by an air burst part of a comet that impacted Switzerland,

          Tunguska almost took out London, except Earth’s rotation placed the air burst over Siberia…

          We have massive space rocks passing close to earth between the Earth and the Moon.

          Better to put the $1-2 Trillion yearly spent of Climate Change, into Space defense…

  13. It’s time to take the show to the Moon,

    One Earth defense strategy is not burdened with warhead concepts or frivolous accessories. It makes use of our Cold War and NASA expertise but contains no actual warhead. It is directly tied to Apollo and gaining a permanent foothold on the Moon.

    To divert or destroy a threatening object with any assurance, you must do to it what it is trying to do to you, first. Kinetically impact it by sending an armada of smart heavy things to meet it soonest with as much multiplicity, precision, combined mass and anger, as possible. Each ‘thing’ is a rocket launched from a battery on the Moon, carrying a heavy mass-payload of simple lunar dust. Each must operate alone, or swarm intelligently to avoid others or meet objectives such as targeting a part of the object (if that is even possible) or flying in formation to coordinate moment of contact.

    But here’s the key: there must be hundreds, even thousands of them… each loaded with ballast and ready to fly at a moment’s notice, receive a mission en route. The armada must form waves, each salvo capable of re-assessing last-minute objectives without delay of communication with base… such as a ‘re-swarm’ to target individual fragments of an object as it splits.

    We supply the technology, the Moon supplies the mass, a place to stand, and light gravity to launch a populous armada with least fuel. Every developed country must help build this. It must be standard and modular, and should be functional soon. This is what humans must do to protect their cherished worlds.

  14. I think we’re being sized up for a humanity-shattering SMOD impact in the near future. First, the Russian bolide. Then, Oumuamua, looking in the artist’s depictions as nothing less than the planet-shattering Doomsday Machine, though admittedly much smaller, came zooming merrily through the Solar System like Arthur C. Clark’s “Rama”, made a quick gravity turn around the Sun (no doubt getting a lot of information on our Sun’s nuclear reactions as it passed) and then sailed away, back to interstellar space, never once approached by human spacecraft or pinged by radar, even.

    Probably kicked into warp drive as soon as it was sufficiently far away.

    Then we had a spate of green comets. GREEN COMETS. Whoever heard of a green comet before? But Space.com was right on the story: “See Two Bright-Green Comets in 2018’s Night Sky: How, Where and When to Look”.

    Never heard of a “green comet” before, and now two of them.

    Yesterday, in Washington, DC, a fireball streaked across the sky, and looked like it almost reached the ground.

    Our space defenses are being tested, and we are woefully unprepared

  15. I thought NASA’s plan was to destroy the economy through the green new deal, and then once there’s no money, we’ll be too busy living in the stone age to care about asteroids.

  16. Given how late many NEOs are discovered, there is almost no hope of deflecting them. However, if they can be broken up early with an explosion-perhaps heating by laser to cause cracking by thermal expansion, then the smaller pieces ablate more substantially. A single large impact can cause more damage than a number smaller impacts. If the speed at impact is below 5 km per second, the bolide does not explode (typically to 8 times the diameter of the impactor.) A number of large blocks crashing to the ground without vaporising on impact and causing the explosion will cause damage so microscopic as to not fretting at all. A large air burst will have local impact, but not total devastation. A series of minor air bursts from a prematurely shattered bolide will have no single aspect that causes major damage.
    As the breakup will be near earth, the air burst/ impact region will be relatively small.
    A single large impact that breaches the mantle will cause a massive rupture on the other side of the planet and the vulcanism that will ensue will make humans extinct. Massive post nuclear winter and sulfides in the atmosphere will cause total crop failure for years- no hope of survival. How long could you survive in some underground bunker? Even after a few years, how would you re-establish the human race?

    • It is physically impossible for a bolide to reach the earth at less than 11 km per second. And a number of smaller impacts or large airbursts would not necessarily be less destructive than one large impact.

      And a impactor large enough to “breach the mantle” will cause extinction-level damage even if broken up.

  17. I am beginning to wonder whether I have a problem with scepticism when organisations set out their stall for a fundraiser:

    “The trick is spotting the near-Earth objects first”
    “so in our search efforts we’ve focused on finding NEOs when they are further away from Earth”

    All bases covered, then. Perhaps it’s just me.

  18. The damage from the Chelyabinsk superbolide was caused by the shock wave it created as it passed through the atmosphere toward its impact site. It also blew off several layers of its outer shell, which is visible in videos taken as it passed. Once that was done, its “trail” disappeared and it became nearly invisible itself, since it was no longer a fireball. It was about the size of a 6 story building, and it broke up as it passed through the atmosphere. Pieces were found around Lake Chebarkul, 43 miles (70 km) north of Chelyabinsk.

    It did NOT explode on impact. That is incorrect. There is a large collection of videos from Russian dashboard cameras showing what it did as it passed and how long the breakup trail was.

    The Chelyabinsk meteor entered Earth’s atmosphere over Russia on 15 February 2013 at about 09:20 local time (03:20 UTC). It moved at a speed of 19.16 ± 0.15 kilometers per second (60,000–69,000 km/h or 40,000–42,900 mph) – well above the speed of sound (600 MPH). That alone would break windows, set off car alarms, and cause a lot of property damage. It broke apart 12 to 15 miles above the Earth’s surface, NOT on impact. There are pieces of it scattered along its trail that still haven’t been found.

    If you’re looking at your homeowners insurance for coverage for rocks from outer space, it’s considered an “act of God” and you’re out of luck. But you can probably pay for any damages if you find the pieces and sell them to meteor hunters.

  19. “Asteroids and comets are warmed by the sun and so glow brightly at thermal wavelengths ”

    Are they 33C (59.4F) ‘cooler’ than if they had an atmosphere?

    Let’s apply some of the available science to derive an answer:

    CAGW Law #1 – Random Climatic Mutation

    That doesn’t get us very far, is there a second Law?

      • tty: “They are close to being perfect black bodies so Stefan-Boltzmanns law applies.”

        Ok, let’s get started. What if the asteroids and comets are 3 dimensional?

  20. Would there be any benefit in putting a satellite in orbit between Earth and Mars to make the same observations? The idea is that observations can be correlated to the Earth observations and create a 3-dimensional view of the objects and their orbits to better determine their possible intersection with the Earth? And the advantage of a different point in space that could pick up dim objects not as easily detectable from Earth.

    • If anything it would complicate matters. Since the satellite would be seeing the objects from a completely different viewpoint and their 3-dimensional position is not known initially it would be difficult to find them from Earth. And remember, over 6 months the viewpoint of an earth- or near-earth telescope changes by 2 AU. That’s plenty for earth-crossers.

      The only case I can think of where a distant viewpoint would be worthwhile is to discover incoming comets that are on the other side of the sun from Earth.

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