It is a cold January afternoon on the peak of Mt. Bigelow, an hour's drive north from Tucson, and the wind burns my face as I watch the colors of the desert sunset bleed into the foothills of the Catalina mountains.
This is the home of the University of Arizona's Catalina Sky Survey, a secluded astronomical observatory whose mission it is to discover and monitor Near Earth Objects (NEOs), comets and asteroids which pass within roughly 120 million miles of Earth's orbit and therefore have the greatest potential to obliterate humanity.
I traveled here with Eric Christensen, a University of Arizona scientist and the principal investigator for the survey, who is letting me tag along to observe for an evening. Christensen is 37, easy-going, and soft-spoken, with dark eyebrows accentuated by his shaved head. We unload groceries from his truck and haul them into the cramped combined kitchen-bedroom where he will be based for the next three nights while scanning the skies for NEOs—weather permitting, of course.
After he stores his groceries, Christensen and I watch the sunset and the mass of thunderclouds amassing on the horizon. "It's not looking good," he says.
Arizona gets around 300 days of clear skies a year and as luck would have it I happened to pick one of the few stormy nights to participate in an activity that demands perfect visibility.
"The effects of an impact, even a comet or asteroid of a modest size, would be devastating."
Christensen's phone rings; it's his four-year-old daughter calling to say goodnight. He disappears into the observatory for a few minutes and then comes back outside. He takes another look at the sky as night descends, beckoning me indoors in the hope that we might be able to run some observations before our view is totally obscured by thunderheads.
For an outpost tasked with preventing mass extinction, the pace is certainly relaxed here at Catalina.
THE BIRTH OF SPACEGUARD
Until a few decades ago, the powers that be didn't take the threat of asteroids very seriously. This changed on March 23, 1989, when an asteroid 300 meters in diameter called 1989FC passed within half a million miles of Earth. As the New York Times put it, "In cosmic terms, it was a close call."
If 1989FC had hit Earth, it is unlikely that many humans would have survived the post-impact fallout. Perhaps more frightening than its proximity was the fact that we had no idea it was even coming. The existence of the asteroid wasn't discovered until eight days after it had zipped by at around 46,000 mph.
After this arguably close brush with total annihilation, Congress asked NASA to prepare a report on the threat posed by asteroids. The 1992 document, "The Spaceguard Survey: Report of the NASA International Near-Earth-Object Detection Workshop," was, suffice it to say, rather bleak.
If a large NEO were to hit Earth, the report said, its denizens could look forward to acid rain, firestorms, and an impact winter induced by dust being thrown miles into the stratosphere.
In the initial moments following impact, the impact site—which is generally 10 to 15 times the size of the asteroid—would be vaporized. Plants and animals would be subjected to scorching heats for about half an hour and a "continent wide fire-storm would ensue." The entire Earth would plunge into perpetual darkness, thick clouds of dust blotting out the sun for months on end. Temperatures would drop by dozens of degrees centigrade while the Earth was covered in this cloud, and when this cloud eventually does disperse, an enhanced greenhouse effect from water vapor trapped in the air could raise surface temperatures as high as 10C above pre-impact levels.
To head off such an ignominious end, NASA recommended forming an alliance of universities and observatories informally dubbed "Spaceguard" in a nod to Star Trek. This alliance would be tasked with identifying asteroids expected to cross Earth's orbit.
The size of an object necessary for such apocalyptic results is on the magnitude of several kilometers in diameter. This is on par with the size of the asteroid that some scientists believe wiped out the dinosaurs around 65 million years ago, which is believed to have been about 9.6 km in diameter. Its impact, which left a 177 km crater off Yucatan Peninsula, likely created an explosion of energy roughly equivalent to that of a million megatons of TNT.
Despite the terrifying prospects of a collision, NASA didn't formally adopt the 1992 survey's recommendations until 1998. Then, prompted by a Harvard astronomer's (erroneous) prediction that an asteroid would pass within 30,000 miles of earth in 2028, it announced the formation of the Near Earth Object Observation program (NEOO), charged with finding 90 percent of NEOs with a 1 km diameter or greater within a decade.
While NEOO is the name of the official program, many of its members still refer to the alliance of observatories as Spaceguard. Today, Spaceguard includes a number of observatories, including Christensen and his team of four other observers at the Catalina Sky Survey, the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) in Hawaii, the University of Arizona's Lunar and Planetary Laboratory SpaceWatch at Kitt Peak, and the Near Earth Asteroid Tracking (NEAT) observatory in California.
Despite the risks, using nuclear devices to deflect asteroids is still being considered as a viable option
In 2005, Congress expanded Spaceguard's mandate to include the discovery of 90 percent of all NEOs with diameters larger than 140 meters by 2020, no small task considering it is estimated that half a million such objects exist in our solar system.
While these objects are significantly smaller than the original targets of the program, they still have the potential to wreak havoc at local and regional levels.
"The entire Earth, rotating on its axis every day, is exposed to these hazardous comets and asteroids," said Dan Mazanek, a senior space systems engineer at NASA's Langley Research Center. "The effects of an impact, even a comet or asteroid of a modest size, would be devastating."
About two years ago, Earth experienced firsthand the kind of damage that can be caused by a small NEO—and it didn't even hit the ground.
On February 13, 2013, residents of Chelyabinsk, a Russian city of 1 million near the Kazakhstan border, received an unexpected visitor from space. At around 9:30 in the morning, residents cast their eyes upward in amazement as a bright ball of fire with a thick trail of smoke streaked across the sky. Traveling at approximately 40,000 mph when it entered Earth's atmosphere, the meteor burst at an altitude of about 97,000 feet and released about 500 kilotons of energy—roughly 25 times more energy released by the atomic bomb dropped on Hiroshima.
Not only was the meteor's arrival something of a surprise to scientists and civilians, it also managed to injure at least 1200 people in the fallout produced by its shockwave.
Such damage must've been the result of a pretty huge meteor, right? Not at all—this meteor was only around 20 meters in diameter.
Video of fallout from the Chelyabinsk collision.
The event underscored the practical importance of cataloging and monitoring smaller NEOs, especially since the meteor was well under the threshold set by NASA for monitoring.
"I think there are a lot of people that are becoming aware of the impact hazard. But it makes it difficult if you have something that occurs every hundred, thousand, ten thousand or million years," said Mazanek. "It becomes increasingly harder to rationalize or to internalize the threat. But when it happens it'll change the world. The Chelybinsk air burst certainly changed the lives of people in that area and I think it brought awareness to the impact hazard in the modern day."
Chelyabinsk made the threat of an NEO impact feel very real, but many researchers caution against the tendency to sensationalize such an incident. "People like to take the Chelyabinsk impact and say 'well, if it came at a little bit steeper angle the effects would have been a lot worse'—but you can take any event and arbitrarily make it worse," said Christensen. "If we had known about the Chelyabinsk object, say ten years in advance, I really doubt we would have done anything about it, other than study it very carefully and evacuate people. It's a tricky line to walk because you don't want to overhype it, but you certainly don't want to minimize what could be a very real risk as well."
BLOBS ON A SCREEN
Back at Catalina, it didn't look Christensen and I would be contributing any NEO discoveries this evening. By the time it was dark enough to observe, the clouds had rolled in. Perhaps sensing my disappointment, Christensen suggested we run some simulations instead. "You're really not missing much exciting," he says as he fires up the computer program. "It's not like you're getting super high resolution photo of asteroids while you're doing this—look."
The screen has come alive with a mess of square tiles, each numbered and corresponding to one square degree of the sky. When Christensen clicks on one of the tiles, a faint, black, pixelated blob can be seen moving across a background of static. That, he tells me, is what discovering an asteroid looks like.
When the team discovers one of these blobs, they track it for about an hour, taking pictures at regular intervals to measure its movement and help determine its trajectory for follow-up surveys.
The process of discovering NEOs is a painstakingly slow one, which make sense given the size of the observation field (the entire sky) compared to the size of the objects being sought after (asteroids between 140 and 1000 meters in diameter).
At Catalina, the main survey telescope has a field of view which covers approximately one square degree of the sky at a time—to put that in perspective, the radius of a full moon is about one half of a degree—and is nonetheless considered one of the largest survey telescopes in operation.
"We don't know where the Near Earth Objects are, however we know where, historically, it is good to find Near Earth Objects," said Christensen. "Some people liken this to looking for your keys under a streetlamp, but the analogy of the keys kind of breaks down because it's not just one set of keys you're looking for, it's one of a thousand keys."
Despite the challenges, the Catalina survey manages to discover about 600 new NEOs a year, which made it the most efficient operative survey until it was surpassed by the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), a Spaceguard member in Hawaii, last year. Out of the total 1,477 NEOs discovered, Catalina found 617 and Pan-STARRS picked up 620.
TAKING THE SEARCH TO SPACE
Despite Catalina's history of successful NEO discovery, there is only so much data that is possible to gather from the surface of Earth. That's why some are now are pushing for space-based detection systems.
"The idea is that if you had a dedicated mission that was exclusively devoted to NEO surveying, you could find objects that were difficult to find from the ground," Christensen explained.
Space-based systems are unaffected by terrestrial weather and light and can scan the skies constantly. They can also use techniques such as infrared scanning, which is severely limited on Earth due to the warm atmosphere.
The B612 Foundation, a US NGO dedicated to protecting our planet from asteroids strikes which is independent of NASA's NEOO program, is in the process of building the Sentinel Space Telescope which it plans to place in orbit to expedite the process of NEO discovery. According to the Foundation, Sentinel is scheduled to be launched atop one of SpaceX's Falcon 9 rockets in 2016 and once in orbit will be capable of detecting 90 percent of all NEOs greater than 140 meters in diameter.
Similar projects are already underway at NASA, including the Wide-field Infrared Survey Explorer (WISE), which has been scanning the cosmos for asteroids on a collision course with Earth since it was reactivated in 2013 after a two year hibernation, and NEOCam, a proposed infrared telescope whose orbit would allow it to survey for objects both in- and outside of Earth's orbit.
These space-based detection systems are especially good at picking up long-period comets, or comets that take over 200 years to complete an orbit around the Sun.
Unfortunately for the future of the world, the effort to find life-threatening NEOs appears to be floundering due to organizational and funding challenges
"Long-period comets by their nature come in from the outer reaches of the solar system," said Mazanek. "They represent a small percentage of the number of [near Earth] objects, but dealing with those is a different problem because you might have a warning time on the order of months or years versus potentially decades with an asteroid."
There is a sense of urgency that comes across when speaking with Mazanek that was absent in my conversations with Christensen. While Mazanek certainly avoids sensationalizing the danger, he has also spent plenty of time professionally contemplating the consequences of such a collision, which has understandably made him anxious to see more work being done in the field.
To date, well over 12,700 NEOs have been discovered and catalogued—an impressive feat. Yet knowing trajectories is not of much help if we don't have a way to deflect them in the event that one comes barreling toward us.
"The hazard is real," said Mazanek. "We have been hit before and we will be hit again."
AN ASTEROID IS HURTLING TOWARD EARTH. NOW WHAT?
In the 1998 film _Armageddo, a team of NASA scientists plans to detonate a nuclear bomb on an asteroid, splintering it before it hits Earth. As it turns out, this scheme isn't that farfetched.
On a sultry May day in 1995, a handful of US and ex-Soviet nuclear scientists and space engineers convened at the Lawrence Livermore National Laboratory just outside of San Francisco for the Planetary Defense Workshop, a conference dedicated to discussing the greatest extraterrestrial threats to Earth and how to avoid them.
Among the prestigious conference attendees was Edward Teller, the father of hydrogen bomb. At one of the sessions, Teller broached the feasibility of placing a one-gigaton nuclear device into orbit. Such a device would be capable of destroying NEOs up to 1 km in diameter and deflecting extinction event class NEOs of 10 km or more.
Despite the counterintuitive nature of placing a massive nuclear warhead in space to avoid catastrophe, Teller's suggestion actually makes a lot of sense—at least on paper. According to one NASA study, nuclear solutions to asteroid deterrence were shown to be between 10 and 100 times more effective in deflecting asteroids than their non-nuclear alternatives.
Yet in spite of its efficacy, the nuclear solution understandably remains highly controversial. The United Nations has banned nuclear weapons in space. While this warhead would be used for peaceful purposes, the fact of the matter is we would still be putting a nuclear bomb into orbit.
Despite the manifold benefits of using nuclear weapons to mitigate collision course asteroids (such as ease and speed of deployment and overall efficiency), there are several downsides to their use. For instance, many NEOs are actually conglomerates of asteroid fragments, "rubble piles" loosely held together by gravity. In these instances, deploying a nuclear explosive could shatter the NEO, effectively creating radioactive cosmic buckshot which could rain down on Earth.
Despite the risks, using nuclear devices to deflect asteroids is still being considered as a viable option.
At a NASA Innovative Advanced Concepts conference in early 2014, Bong Wie of Iowa State University's Asteroid Deflection Research Center proposed sending a spacecraft to intercept an asteroid, deploying a kinetic impactor to create a hole in the asteroid, and sending a nuclear warhead on the tail of the kinetic impactor. He has received $600,000 in grant funding from NASA to develop the concept of this "Hypervelocity Asteroid Intercept Vehicle," suggesting that there is still a considerable amount of interest in nuclear strategies.
Nevertheless, the non-nuclear deflection methods far outnumber their nuclear counterparts.
In 2010, the US National Research Council (NRC) commissioned a report examining current NEO surveys and potential strategies for avoiding NEO impacts in the future. The strategies outlined in the study and those proposed independently by other scientists range from the astoundingly mundane to wildly futuristic: everything from clouds of steam placed in the NEO's trajectory to the use of solenoids, in which iron rich NEOs become the core to a giant electromagnetic coil placed in their orbit, effectively arresting their progress.
Many space agencies advocate the use of non-nuclear kinetic energy to knock an NEO off course using a high-mass spacecraft or even another NEO as an impactor. In a 2007 report, NASA dubbed the non-nuclear impact strategy as the "most mature approach" to NEO deflection, despite nuclear impactors proving to be wildly more effective deterrents.
The Deep Impact mission, launched in 2005, was a prime example of the kinetic strategy. NASA launched "a coffee table sized impactor at a city sized comet," which helped scientists determine the porosity and chemical composition of comets in deep space. It also was the first kinetic impactor to be successfully tested in space, something which may prove crucial to asteroid deflection research in the future.
Another technique is surface ablation, which essentially makes use of concentrated energy to produce a coherent beam which heats the surface of the NEO, effectively turning a solid into gas.
This can be accomplished in two ways, one of which makes use of lasers and the other which uses concentrated solar power, similar to the way a magnifying glass can be used to start a fire.
Besides the technological challenges, there is another, far more dubious downside common to both types of surface ablation: their potential to be used for nefarious purposes, like wiping out civilian populations with space lasers.
Another potential tool in NASA's hypothetical toolbox is the mass driver, a futuristic propulsion system which is most succinctly described as an "electromagnetic catapult."
In essence, mass drivers were conceived as a method of launching spacecraft which foregoes the use of rockets in favor of a linear motor to accelerate launch objects to high speeds. Mass drivers could be placed on asteroids, launching material from the asteroid into space along predetermined trajectories. This would not only alter the asteroid's orbital path by decreasing its mass, it would also alter its course by way of the backward thrust created by launching this material into space.
So, any problem with mass drivers?
"When you throw the material off, you have to throw it in the direction that is conducive to changing the object's orbit in the way you want to," said Mazanek. "Asteroids rotate, meaning you want to wait until you're at the optimal orientation before you expel the material to get the effect. So you have inefficiency because you don't know what that rotation is—it could be tumbling, completely random."
Mass drivers are also relatively large and complex systems. Depending on the circumstances, it could take years to install robotically on an asteroid, time that may simply not be available if an asteroid is bound for Earth.
The final option for asteroid deflection is the gravity tractor. The basic idea here is to have one or multiple spacecraft hovering above an asteroid, using their gravitational attraction to slightly divert the NEO's trajectory. While this NEO deflection option is certainly appealing insofar as it is the least destructive, it also requires the longest amount of warning time to pull off, given the miniscule orbital changes that a spacecraft would be able to exert gravitationally.
DELYAS AND DISORGANIZATION
The European Space Agency is currently working with NASA on an Asteroid Impact and Deflection Assessment (AIDA) mission to launch in 2020 to test whether or not a spacecraft is able to deflect an asteroid from a collision course with Earth. AIDA is aiming for 65803 Didymos, a binary system in which a larger asteroid is orbited by a smaller counterpart. Should it meet its originally proposed 2020 launch date, AIDA will impact the asteroid sometime in October of 2022.
The mission will consist of two vehicles, one which is meant to simply monitor the asteroid and assess the results of the mission, the other appropriately called the Double Asteroid Redirect Test (DART), which will essentially be employing a "kinetic" strategy: ramming itself into the smaller asteroid to gauge the effect of an energy transfer.
AIDA's success would mark the first intentional asteroid deflection mission. Unfortunately, it's still in the planning stages. Despite being in the works since 2012, the mission still lacks a development and launch schedule.
The status of AIDA reflects a widespread problem with the NEO mission. Unfortunately for the future of the world, the recent 2005 Congressional mandate to find NEOs on the order of 140 meters or larger within the decade appears to be floundering due to organizational and funding challenges.
"The Earth is likely to get hit by an asteroid at some point in the future."
After reports from the National Research Council made it clear that meeting the discovery requirement outlined in the Congressional mandate was impossible given the lack of program funding, NEOO got a tenfold budget increase from 2009 to 2014. Yet it still faces a number of difficulties. A program audit released last September described the NEOO program as a one-man operation that is poorly integrated and lacking in objectives and oversight.
Lindley Johnson, who was the only NASA employee working in the office until 2014, feels that assessment is slightly unfair.
"I think we actually have a pretty well integrated team. This was a program unlike [the auditors] had ever seen, quite frankly," said Johnson in a thick Texan drawl.
However critical the audit may have been, Johnson acknowledges that it has produced results. "There is some additional manpower that's being brought under my auspices, and I have a couple of scientists and program executives working for me under the new structure," he told Motherboard.
As for the alleged lack of integration, Johnson feels that this is simply the nature of the program.
"[The NEOO Program] is and always will be a loosely structured and coupled program because we take advantages of a number of capabilities around the world which already exist, rather than starting everything on our own," he said, referring to the decentralized observatories that make up Spaceguard. "There actually aren't any NASA personnel who run these projects."
The funding was used to hire extra help at the NEOO office (there are now 3.5 full time employees, including Johnson), and dedicate more resources to finding NEOs. Based on Johnson's numbers, the investment has shown results: in 2014, over 1,400 NEOs were discovered as compared to 1,000 the year prior.
Even with the extra funding, Johnson said, the program is still falling behind its goals. He estimates only about 15 percent of NEOs of 140 meters or larger have been discovered, acknowledging that the program will not meet the Congressionally mandated goal of finding 90 percent of these asteroids by 2020.
"What it takes [to find all these objects] is a more capable system," said Johnson. "To meet the goal in the time frame of a decade or two…really takes more capability than we have the funding to field right now."
THE WAITING PLACE
There is no debate that a large asteroid impact could end life on Earth as we know it. Given that the most recent "near misses" caught observers off guard, you'd think future investments in surveying and deflection of asteroids would be an easy sell.
The problem is that the natural hazard posed by NEOs is one that develops on an evolutionary or geologic time scale—in other words, incredibly slowly. Humans aren't wired to comprehend such threats, and the levelheadedness with which Christensen and other observers talk about NEOs may be undercutting their mission.
"I cringe every time I hear somebody talk about the asteroid impact risk as some sort of existential threat to humanity," said Christensen. "On some level that's true—if you want to take a really long view and look over the next hundred thousand years, sure, asteroid impacts are something you need to consider. It's very easy to oversell and I almost tend to take the other tack and almost minimize the risk maybe more than I should. The Earth is likely to get hit by an asteroid at some point in the future—in fact the Earth gets hit by asteroids every day, but the ones that hit us every day are so small they're not even considered considered asteroids—they're meteoroids. This is an ongoing effect that has… shaped the evolution of life on Earth, and will continue to be an evolutionary force in the near future."
"The fact is, with current technology we can identify threats well in advance and that's important. If we can do something like that with a relatively modest investment, it seems to be worthwhile."