One of the most frustrating questions I’ve had to deal with when making public presentations on the planetary defense and asteroid impact issue is “what can I do to help?” The issue of asteroids impacting Earth is so far outside the experience of most people, and the “solutions” so arcane and technical that identifying anything a regular person could do that would really be helpful has just been beyond me.
Well that has now changed and I couldn’t be happier! The answer is… sign the 100x Asteroid Day Declaration. Really!? Yes indeed, and I hope to tell you why in this blog.
I think that everyone understands that you can’t protect yourself if you don’t know what’s coming at you. Early warning is the sine qua non of planetary defense. In earlier blogs I’ve gone into the population of objects out there, circulating around the Sun, minding their own business, which can cause death and destruction if they were to impact Earth. To shorten it dramatically there are approximately 10 million NEOs out there of the Chelyabinsk impactor size and 1 million objects out there of the Tunguska impact size. Of all those millions of objects we have, to date, discovered less than 1% of the Tunguskas and less than 0.1% of the Chelyabinsks. In other words, at the moment, the probability is over 99% that we’ve never seen, let alone tracked, the next object of Chelyabinsk size or larger that’s going to hit us.
Now let’s put this in perspective. NASA, the telescope teams it supports, and a few others, have done an excellent job in finding and tracking the larger, far more dangerous objects that can do continental or global level damage. In fact, since 1998 NASA has discovered over 95% of the objects larger than 1 kilometer in diameter that would cause global devastation if they were to hit. These comprise the largest 1,000 or so of the over 12,000 NEOs that have been discovered to date.
That’s great… but those objects hit only about once every 500,000 years! How about the ones that hit every 50 years or several hundred years? Most people who look seriously at this issue realize that what we want to know about and be able to prevent are impacts from all the asteroids out there that could cause death if we permit them to hit. Preventable death.
The 20 meter diameter Chelyabinsk asteroid came very close to causing death on the morning of 15 Feb 2013. Experts have concluded that had it come in just a bit steeper than the 16 degree dive angle it followed it might well have killed people. And the 40 meter Tunguska NEOs, deemed “city killers” by the U.S. Congress in a hearing on planetary defense, would likely kill millions if one were to impact directly over a major city. This is, of course, highly unlikely, even if one were to impact given the 70% of the Earth’s surface that is ocean and the low average density of cities on the solid land. Still, do we want to continue to run around with our eyes closed (effectively) and have one arrive unannounced? Surprise!! I’m here! All 30 Hiroshima equivalents (Chelyabinsk) or 267 Hiroshimas of me (Tunguska)! I don’t think so.
But time is an issue here. At the current rate of discovery of 20 meter NEOs and larger, about 1000/year, it will take over 1,000 years to find 1 million new NEOs. That’s a long time and even then we’d have reached only 10% or so of the Chelyabinsk objects that potentially threaten impact. This then is the reason why when Asteroid Day was first discussed we came up with a goal of 100,000 (or 100x) new discoveries per year, within ten years. We’ve simply got to get at it!
Can this be done? Is it possible to make this goal? When it was initially discussed it seemed possible, but a real reach. Happily it now seems to be quite possible indeed, given a recent decision and assuming a positive outcome on other decisions to be made in the near future. And that’s just where you, and your signature on the 100x Declaration come in.
So what’s happened? The first key event was the NSF funding commitment to the construction of the LSST (see “Future Asteroid Surveys…” http://www.asteroidday.org/learn/ and http://www.lsst.org/lsst). This 8.4 meter ground-based survey telescope will be a tremendously capable NEO discovery machine after it becomes operational, hopefully in 2022.
As to the additional key decisions I mentioned, the first among them is the selection to be made over the next year or so for NASA’s next Discovery science mission. Among the 28 candidates competing for this funding is NEOCam (see http://neocam.ipac.caltech.edu), an infra-red space telescope with great capability for discovering NEOs. NEOCam would be placed in a unique location in the space referred to as L1 (Lagrangian point #1), located about 1 million miles from Earth in the direction of the Sun. The unique feature of this location is that L1 (and NEOCam) stays in that relative position as the Earth orbits the Sun. Unlike LSST which relies on sunlight reflected from the asteroids, NEOCam will be above the atmosphere looking for NEOs using the heat radiated from the asteroids it discovers. This is a powerful capability only available to space-based telescopes and it will enable NEOCam to complement the discoveries made by LSST.
An alternative to NEOCam is the Sentinel IR space telescope being championed by the B612 Foundation(seehttp://sentinelmission.org). While Sentinel’s eyes, similar to those of NEOCam, will detect the heat radiated from asteroids, it would be located in a very different place in space. Sentinel would be placed in an orbit around the Sun between the Earth and Venus. In this orbit Sentinel would move around the Sun slightly faster than the Earth, looking outward from the Sun and scanning for asteroids that cross the Earth’s orbit. Unlike NEOCam Sentinel will spend the bulk of its time looking at portions of the Earth’s orbit not visible from Earth and it will therefore experience less overlap with LSST in its discoveries than will NEOCam. Additionally, because it is moving around the Sun faster than the Earth it will more readily discover asteroids that have an orbital period very near 1 year. These very important NEOs are only seen by “Earth locked” telescopes (ground or space based) on an infrequent basis.
The bottom line here is that the combination of the LSST and either NEOCam or Sentinel will be very powerful in discovering the 99% of dangerous NEOs that we don’t now know about. And either space telescope, in combination with the ground based LSST, will approach or exceed the 100,000 NEO discoveries per year that are called for in the Asteroid Day 100x declaration.
So why is your signature so important? Because neither NEOCam nor Sentinel is yet funded and without one or both of them to work along with LSST we will be locked for decades into knowing only a small fraction of the asteroids out there that can cause death on impact. LSST alone will make a pretty good dent in the larger sized asteroids that are missing in our inventory. Over its lifetime it will probably reach or approach the current Congressional goal of discovering and tracking 90% of the NEOs larger than 140 meters in diameter.
But planetary defense, in my book, necessitates knowing all of the NEOs out there that are likely to to cause human death on impact. That translates into discovering all of the asteroids larger than 20 meters in diameter (think Chelyabinsk, about 30 times the explosive power of the Hiroshima bomb) that are in those orbits most likely to impact earth (the so-called “impactor population”; see sidebar).
The Sentinel team has calculated that, in combination with LSST, and by focusing on the smaller objects, they can discover, in 10 years of coordinated observations, over 80% of the 40 meter (Tunguska) population and over 45% of the 20 meter (Chelyabinsk) population. They have also estimated the productivity of a similar cooperative observing program between LSST and NEOCam, and it is not far behind.
This is an amazing breakthrough potential and I believe a truly unique opportunity. With LSST funded and two viable candidates for a companion IR space telescope to work with it we can come very close to having, in the next 10-20 years, a full inventory of the NEOs out there that could cause loss of life. (remember… unnecessary loss of life!) If, that is, we act now. Remember, this is cheap! What we’re talking about here is approximately three tenths of one percent of the NASA budget over 10 years!
If NEOCam is selected in the Discovery mission process over the next year, we can all cheer and anticipate the exciting results. However, if it is not the winning candidate in the Discovery selection then your signature, along with (hopefully) a million like signatures on the Asteroid Day 100x Declaration will go a long way to insuring that the Unites States and/or other nations and their space programs will initiate and fully fund a dedicated infrared space telescope to capitalize on this unique opportunity to fully inventory the life-threatening asteroid population.
What greater gift could we possibly give to the future of life here on Earth? We can do this… and do it now. To make certain your signature counts please register below so that we can personally notify you as soon as the petition system is set up. And when you are notified, please join the initial signers of the100x Declaration and add your signature to let our governmental leaders know that we want this done!
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