Asteroid Day 2018: Planetary Defense Progress Report

Earlier this month, the White House released a report detailing the current status of planetary defense efforts in the United States. The report discusses the ways that US government agencies would respond to an anticipated or unanticipated impact event, and outlines the steps that they should take to mitigate the danger. Unfortunately, this is just a report—any policy changes or future missions will require further action from the President and Congress.

This was a heartening but also concerning admission ahead of Asteroid Day. I’m encouraged that America is taking planetary defense seriously. Protecting against asteroid and comet impacts is arguably the single most important thing that we can be doing in space right now. However, it has not been the primary or even secondary focus of any major space agency. Much of the work has been limited to university researchers and private-sector organizations.

On this day, the 100th anniversary of the Tunguska Event, I would like to discuss our progress in planetary defense. While NASA and other organizations have done an excellent job tracking near-Earth asteroids and assessing their threat to humanity, we are not dramatically closer to impact prevention capabilities. Nevertheless, there is reason to be cautiously optimistic. Let’s discuss the major ongoing and future missions to explore and detect asteroids that could potentially threaten Earth.

To begin: just this week, the Japanese Hayabusa2 spacecraft arrived at the asteroid 162173 Ryugu. For the next eighteen months, Hayabusa2 will orbit the 900-meter-wide space rock. In addition to orbital observations, Hayabusa2 will release several surface probes and retrieve samples for return to Earth in late 2020. These samples will include material taken from the interior of the asteroid, extracted by detonating a small explosive device on the asteroid’s surface.


Hayabusa2 performs surface sample extraction at Ryugu.

Source: JAXA

Hayabusa2 is primarily focusing on planetary science, with consideration for eventual resource extraction. However, understanding the structure and dynamics of near-Earth asteroids is essential for predicting their impact odds and planning redirection maneuvers if need be.


Asteroid 162173 Ryugu as imaged on June 26.

Source: JAXA

Planetary defense is a major motivation of the OSIRIS-REx mission, which is continuing on its way towards asteroid 101955 Bennu. Astronomers estimate that there is a small chance that Bennu may impact Earth in about 200 years, so studying the asteroid up-close will considerably refine their calculations.

(Before someone asks: OSIRIS-REx Principal Investigator Dante Lauretta wrote a blog post specifically outlining the damage that Bennu would cause if it were to impact Earth. Note that all recent estimates place the impact odds far, far below one percent.)

OSIRIS-REx launched in 2016 and will arrive at Bennu in August of this year. The spacecraft performed a burn last January to put it on a trajectory for an Earth flyby, which occurred on September 22, 2017. This maneuver put the spacecraft on an appropriate orbit to rendezvous with the small asteroid.

Like Hayabusa2, OSIRIS-REx is also a sample return mission. Allowing scientists to study asteroidial material in laboratories on the ground massively increases the information we can glean from them, because many of the most interesting measurements and experiments are simply too heavy, bulky, or complex to cram within an interplanetary spacecraft.


OSIRIS-REx performs surface sample extraction at Bennu.

Source: NASA

Sample return is just one aspect of the OSIRIS-REx mission. In addition to the standard planetary science objectives, OSIRIS-REx will study the impact of non-gravitational forces on the orbit of a celestial body. Many of these forces are well-understood for conventional satellites, but the data for asteroids and comets is hazy when it exists. Characterizing these effects for objects like Bennu will go a long way towards predicting their orbits and thus the impact odds long-term.

Once we understand these risks, though, we need the capability to deflect any objects we find headed towards Earth. Here the progress has been less inspiring.

First, a mission is currently under development called the Double Asteroid Redirection Test, or DART. Planned to launch in December of 2020 or early 2021, DART will rendezvous with the asteroid 65803 Didymos in October of 2022. Didymos is actually a double asteroid, and DART with collide with the smaller moon when the asteroid is near its closest approach to Earth. Ground-based observers will measure the effect that the collision has on the moonlet, giving researchers some hard data on just how well the kinetic impact technique would work for asteroid deflection.

This is an interesting mission, both for its planetary defense implications and for its technology. DART is expected to be the first spacecraft to test the NASA Evolutionary Xenon Thruster (NEXT), and will sport the Roll-Out Solar Array (ROSA) design tested on the International Space Station in 2017. Unfortunately, there has been some uncertainty over whether this mission would actually fly. Though required by law, it was not included in the 2018 NASA Budget. The John Hopkins University Applied Physics Laboratory, however, has continued working on the project and as of April was discussing final design and fabrication later this year.

On a related note, the Asteroid Redirect Mission (ARM), which the mainstream science media so eloquently described as “giving the Moon a moon”, was recently cancelled in favor of pursuing manned Lunar missions. This is a questionable decision. ARM was a logical development conduit for key technologies in robotics, propulsion, and astrodynamics. All of these would have contributed greatly to manned exploration of the Solar System. Thankfully, much of this technological investment will be preserved, and may eventually pay dividends in planetary science and defense.


ARM grapples an asteroidial boulder to return to the Earth-Luna system.

Source: NASA

Nevertheless, having a six-ton asteroid in Lunar orbit would have provided a compelling intermediate target for human spaceflight. (The Deep Space Gateway would naturally fill the role of an intermediate target, but I’ll save the discussion of its advantages and disadvantages for another day.) Landing is a much bigger challenge than just returning to cislunar space, and the scientific knowledge from returned samples would also have been tremendous.

Another important project has also faltered: the Sentinel Space Telescope. This mission was designed by the B612 Foundation to detect asteroids that Earth-based telescopes miss by putting a dedicated spacecraft in solar orbit near Venus. Sentinel would have launched on a Falcon 9 rocket in 2018 or 2019 and cost $450 million to develop.

This proved way too expensive for a niche non-profit. NASA provided some funding, but this ended in late 2015, and B612 was unable to raise the remainder. Retired astronaut Ed Lu confirmed that the project was dead last year.


Rendering of the Sentinel Space Telescope on-orbit.

Source: B612 Foundation

B612 is instead focusing on telescopes mounted to significantly smaller satellites. They will use a new technique called synthetic tracking to spot smaller asteroids than previously possible. Few and fewer potential “killer” asteroids remain to be discovered as better and better telescopes come online, so the overall emphasis is turning towards the smaller rocks. These can still be deadly: the Chelyabinsk meteor was only about 20 meters across but caused thousands of injuries and millions of dollars in damages.

If mounting space telescopes on small satellites sounds ambitious, consider that the Canadian Space Agency launched a comparable spacecraft called NEOSSat with similar goals in 2013. Small satellites are much more affordable for non-governmental organizations, in part because launch vehicle cost can be distributed over multiple missions—NEOSSat rode to orbit with six other spacecraft. An audit in 2013 estimated the program was significantly over-budget. Total cost: CDN$25 million.

NASA and the Jet Propulsion Laboratory are also pursuing a Near Earth Object Camera, which would join the fleet at the Earth-Sun L1 point. NEOCam was passed over for the latest Discovery Mission opening, though was still under development as of April under the aegis of NASA’s Planetary Defense office. Without a clear funding commitment, though, mission planners are severely limited in developing the program.

This is a bit concerning, because NASA has a Congressional mandate to detect 90% of near-Earth objects 140-meters and larger by 2020. Much of this work was completed by the Wide-field Infrared Survey Explorer during its extended mission. WISE discovered over 3000 asteroids and comets, including 262 near-Earth asteroids. 47 of these are considered potentially hazardous. Detecting the remainder will probably require new hardware, so I’m doubtful that NASA will meet the Congressional mandate. If current legislators are serious abut this mission, they need to allocate funds—and quickly.


Artistic rendering of the WISE spacecraft.

Source: NASA

The probability that an undetected asteroid will hit Earth before that objective is met—on time or not—is low, but every day that passes risks another Chelyabinsk. Only once we know the threats can we take actions to mitigate them. Having the necessary technology ready-to-go would vastly improve our odds.

On the whole, I’m glad to see that the United States is taking planetary defense seriously, but there’s a lot of work left to do. Check back again next Asteroid Day to review the advances we make in the coming months.


Should We Colonize Mars Sooner or Later?

Existential threats to the human species (colloquially known as ‘x-risk’) come at three scales. The widest-scale risks would sterilize the solar system, at least, as a whole. Next are threats which could destroy civilization due to societal or technological incompetence. And at the smallest scale are risks to Earth’s habitability.

If that ordering seems odd, consider a few examples.

Threats in the first category include gamma ray bursts, nearby supernovae, or the disruption of the solar system following an encounter with a rogue star. None of these are considered particularly likely in the near future, and more importantly are centuries if not millennia beyond our capacity to defend against them.

Threats in the second category include superintelligence, runaway nanotechnology, or the development of new pathogens against which existing organisms have no natural defense. While these may seem differentiated from the first category by their origins, this is not necessarily the case. Natural pathogens are potentially just as deadly as man-made ones. Furthermore, none of these phenomena are necessarily extinction-level events—superintelligences and autonomous nanoswarms may decide that human civilization is not an adversary, and leave us alone. This is particularly the case if intentionally constructed by conscientious researchers. Such possibilities point to a separate class of civilizational issues—coordination problems—but that is quite another post.

Threats in the final category include asteroid strikes and supervolcano eruptions. Arguably, these are the most tractable of x-risks. With asteroids, in particular, early detection would allow us to perturb the body’s orbit sufficiently to pass clear of Earth, potentially decades or even centuries in advance. Supervolcanoes represent a trickier problem—our geoengineering is not so far developed to adequately predict earthquakes and volcanic eruptions, let alone attempt to prevent them. But with continued study over the next few hundred years, that may finally change.

There are two plausible positions on the efficacy of space colonization to mitigate existential risks in the third category:

  1. The technological and economic challenges inherent in developing independent off-world colonies will take a very long time to solve, so we shouldn’t bother.
  2. For those very reasons, we should start working on space colonization immediately.

It should not surprise those of you who know me which side of this dichotomy I’m on, but both sides deserve a fairer shake, because the dichotomy is basically false.

For one thing, some money and effort is already expended on space colonization. To be clear, this expenditure is a minuscule fraction of total global production. America spends approximately $19 billion on the National Aeronautics and Space Administration each year, and only a moderate percentage of that total is focused on long-term research1. NASA has a larger budget than any other space agency world-wide, and compared to the Gross World Product of about $75 trillion, we can confidently say that the global expenditure on space colonization is less than 0.03% of the planetary economy.

But even if we halted explicit interplanetary research, the push for more efficient launch vehicles and better medical and agricultural technologies would still represent progress on that front. (Satellite launches won’t end for a long time—you had better believe that Earth observation is critical to managing natural disasters!) When whatever crisis necessitated such a change was finally averted, we would likely be in a better position technologically (if not economically) to pursue off-world colonies.

The crux of the anti-colonization argument, of course, is economics. Can we afford to expend money and effort on space exploration when other problems are supposed to be more pressing? The usual pro-space responses to this question are not terribly good. Let me attempt to give better arguments.

I’ve already made one above, which is that spaceflight consumes a tiny portion of the global production surplus. America alone spends more on education than the world on spaceflight, and it’s not even clear if we’re getting our money’s worth. Those wishing to find the funds for such projects may want to look elsewhere first.

Secondly, the burden of funding astronautics is shifting (slowly!) to the private sector. A few billionaires have gotten tired of competing for the coolest yacht and started competing for the best rocket. Don’t take me for one of the naïve observers who believe space exploration has already been privatized—SpaceX, Orbital Sciences, the United Launch Alliance and all the rest absolutely could not do what they’re doing now without the help of NASA and the Department of Defense, and they know it. But this does represent a shift in the right direction.

Some protest the change on anti-capitalist grounds. I’ve seen a few people say that Elon Musk wanting to colonize Mars is bad, because wealthy individuals would get to escape whatever disaster befalls Earth while the poor perish. I think this objection is foolish for three separate reasons.

Firstly, the sort of person who makes such a criticism is unlikely to support private fortunes to begin with. Obviously, redistribution is their preferred change, but the rich spending their riches on social ends rather than wasting them on mansions is still an improvement. And trying to save humanity is certainly a social end.

Secondly, if a catastrophe does hit Earth, a predominantly wealthy population surviving is still preferable to no one surviving. I have to wonder: do the people who make these arguments entirely appreciate that the question is human extinction?

Let me state that clearly: if you value material equality above the survival of the species, you are no humanitarian.

But the near-term probability of an Earth-only threat coming to fruition is fairly low. In all likelihood, a Mars colony would develop while civilization here continues to exist. Moreover, developing societies from scratch (in multiple locations on Mars, as well as on Luna and the asteroids) will allow us to better comprehend the social problems we’re currently trying to solve. Among the questions that may be answered, will be the role that economic inequality plays in causing other undesirable ends. It may very well be that the billionaires of today are paving the way to something more progressive3.

I don’t think the value of trying out new cultural forms can easily overstated. A major obstacle to solving our problems on Earth is that there’s very little room in which to explore ideas. Succession is illegal in pretty much every country. Taxation and regulation severely limit the space in which experimental communities can be practical4. Of course, Seasteading addresses this particular issue without leaving the planet, but it does not address major planetary risks5, and is unlikely to scale up to the level a colony off-world eventually would.

If we’re taking civilizational threats seriously, we have to decide: colonize Mars sooner or later? To a certain extent, it is an empirical question—what timeline and resource distribution maximizes our odds?—but a question we have to answer on woefully incomplete data.

We don’t know much about the asteroid threat from the inner solar system. We don’t know much about supervolcanoes. We don’t understand the atmosphere well enough to rule out a runaway greenhouse effect. Nor do we understand intelligence enough to predict when or if AI would become a threat, or what the preconditions for a global pandemic are.

For that reason, I advocate increasing work on planetary defense and existential risks across the board—including, yes, space colonization. Now I don’t think that that will be a particularly fast process. Even if landing humans on Mars by 2027 is technologically feasible, founding a colony in the next decade would probably be a suicide mission. There’s just too much prerequisite work to be done.

But that’s true on every front of the fight for our species’ survival. Every year we delay, is a year left to chance. Some argue that the odds are low, because there’s no a priori reason to believe we’re living in a special time6. I reject this argument. There may be no reason to assume that we exist towards the beginning or the end of the human population distribution, but there’s no reason to believe, either, that the last humans will know they’re the last humans until disaster actually strikes. If we’re them (or their parents), well, optimism won’t do us any good.

On the other hand, if disaster doesn’t strike but we’ve cleaned up our environment, created a more resilient infrastructure, developed friendly artificial intelligence, learned how Earth’s interior really works, and colonized the solar system—what a shame. We made a better world, a world that’s now safer and more prosperous than ever, and no threat materialized. Or rather, threats were prevented from materializing.

There’s no deadline, of course, no point after which we’re in the clear. There will always be some risk, even if it’s just from the spontaneous collapse of the universe. But every threat we successfully address leaves humanity better positioned to tackle the next one. Design thorium reactors to end greenhouse emissions, put them in rockets to power advanced propulsion engines. Scale up the rockets we use to deflect asteroids, ride them to Mars. Genetically engineer crops to feed the Martians, send them back to Earth to solve overpopulation. And so on and on, till one fine century we control the stars and save whole systems from destruction.

So let’s get started.


1The vast majority of the agency’s expenditures are on space science2, Earth science, aeronautics, technology research, and supporting operations on the International Space Station. Maintaining a continuously-inhabited station in orbit goes a long way towards preparing for interplanetary missions, but most of the research done on-orbit is focused on more immediate applications such as medicine and materials science.

2Whether lunar, solar, and interplanetary probes count as spending towards eventual colonization probably depends on who you ask.

3I was tempted to write fully-automated luxury communism, but I wouldn’t want to give new readers an incorrect impression of my views. I’m an ex-libertarian more because I support spending 0.5% of the federal budget on space exploration than because I want to nationalize the economy.

4In particular, the requirement to pay county, state, and federal taxes forces more communalist groups to trade on the market, which does nothing to help demonstrate the efficacy of collectivized economic models (or lack thereof).

5That said, Seasteading could prove more environmentally friendly than living on the land. Solar and wind power are practical on such scales, and I doubt seasteaders will waste precious deck area watering grass they’ve no plans to enjoy.

6See Brandon Carter’s Doomsday Argument.

Asteroid Day

June 30 the 108th anniversary of the Tunguska Event, a large explosion which flattened almost 200,000 hectares of Siberian forest. For many years, the cause of the event was controversial, but is now generally agreed to have been a small meteor exploding as it grazed Earth’s atmosphere.

In February of 2013 a similar event occurred, this time near the Russian city of Chelyabinsk. Instead of exploding over uninhabited forest, it injured 1500 people and caused severe economic damage to many, many more. Despite a century of warning, humanity didn’t learn.

Today, I’m asking you to change that.

Meteor explosions release as much energy as atomic bombs. In fact, they are frequently detected by the systems used to watch for illegal nuclear testing above Earth’s surface. Here are the explosions detected during my lifetime, up to the Chelyabinsk event:


Only one of these asteroids exploded sufficiently close to population centers to cause significant damage, but it was only a matter of time until one hit a city. Three years later, we’re no closer to preventing this from happening again.

Asteroid impacts are neither the most damaging nor the most frequent natural disasters. They are, however, the only one which can be prevented by entirely technological means. Given sufficient time and warning, we can deflect an asteroid of any size from its Earth-impacting trajectory. The technical problems are not particularly difficult–such a mission would be simpler to design and execute than some of our more complicated science probes.

No, technology is not the problem. Social will, is. Planetary defense is no ones jurisdiction, and few are willing to take up responsibility for it. The B612 Foundation launched Asteroid Day in 2014  to remind the world that it’s only a matter of time before another Chelyabinsk. Will your city be next?

I’d rather not find out. The more we learn about the asteroid population of the inner Solar System, the more obvious it becomes that humanity is living on borrowed time.

Planetary defense is a species-level concern, and so far there’s been very little effort on the part of governments or the private sector to deal with it. The most promising project to date is the B612 Foundation’s Sentinel Space Telescope, now tentatively scheduled to launch in 2019. Without adequate funding, it will be delayed yet again, leaving Earth vulnerable to sunward asteroids yet another year. You can donate to the project here.

If you live in a democracy, consider writing your legislators about the importance of planetary defense. Protecting Earth from external threats is one of the few things governments should unambiguously be concerned with, but so far very little action has been taken.

Finally, think about joining the thousands of scientists, astronauts, and private citizens who have signed 100X Declaration. To date, we’ve observed about 1% of the estimated Near Earth Asteroids. This petition calls for us to find the rest, quantifying the threat once and for all.