3 Questions: Fortifying our planetary defenses

When people think of asteroids, they tend to picture rare, civilization-ending impacts like those depicted in movies such as “Armageddon.” In reality, the asteroids most likely to affect modern society are much smaller. While kilometer-scale impacts occur only every tens of millions of years, decameter-scale (building-sized) objects strike Earth far more frequently: roughly every couple decades. As astronomers develop new ways to detect and track these smaller asteroids, planetary defense becomes increasingly relevant for protecting the space-based infrastructure that underpins modern life, from GPS navigation to global communications.The good news for us earthlings is that a team of MIT researchers is on this space-case. Associate Professor Julien de Wit, Research Scientist Artem Burdanov, and their colleagues recently developed a new asteroid-detection method that could be used to track potential asteroid impactors and help protect our planet. They have now applied this new technique to the James Webb Space Telescope (JWST), demonstrating that JWST can be used to detect and characterize decameter-scale asteroids all the way out to the main belt, a crucial step in fortifying our planetary safety and security. De Wit and his colleagues recently co-led with with Andrew Rivkin PhD ’91 new observations of an asteroid called 2024 YR4, which made headlines last year when it was first discovered. They were able to determine that the asteroid will not collide with the Moon, which could have had impacts on Earth’s critical satellite systems.De Wit, Burdanov, Assistant Professor Richard Teague, and Research Scientist Saverio Cambioni spoke to MIT News about the importance of planetary defense and how MIT astronomers are helping to lead the charge to ensure our planet’s safety.Q: What is planetary defense and how is the field changing?Burdanov: Planetary defense is a field of science and engineering that’s focused on preventing asteroids and comets from hitting the Earth. While traditionally the field has been focused on much larger asteroids, thanks to new observational capabilities the field is growing to include monitoring much smaller asteroids that could also have an impact.De Wit: When people think about asteroids they tend to think of impacts along the lines of these rare, civilization-ending “dinosaur killer” asteroids — objects that are scientifically fascinating but, happily, statistically unlikely on human timescales. But as soon as you move to smaller asteroids, there are so many of them that you’re looking at impacts happening every few decades or less. That becomes much more relevant on human timescales.Now that our society has become increasingly reliant on space-based infrastructure for communication, navigation technologies like GPS and satellite-based security systems, we can be affected by different populations of smaller asteroids. These smaller asteroids will probably lead to zero direct human casualties but would have very different consequences on our space infrastructure. At the same time, because they are smaller, they require different technologies to monitor and understand them, both for the detection and for the characterization. At MIT, we are working to redefine planetary defense in a way that is far more pertinent, personable, and practical — focusing on these much smaller asteroids that could have real consequences. In other words, planetary defense is no longer just about avoiding extinction-level events. It is about protecting the systems we depend on in the near term.Q: Why are observations with telescopes like the James Webb Space Telescope (JWST) so important to keeping our planet safe?Teague: We’re entering a time now where we have these large-scale sky surveys that are going to be producing an incredible amount of data. We’re trying to develop the framework here at MIT where we can sift through that data as quickly and efficiently as possible, and then use the resources that we have available, such as the optical and radio observatories that we run like the MIT Haystack and Wallace Observatories, to follow up on those potential threats as quickly as possible and determine whether they could be problematic.We’ve been doing trial observations to try and piece together how fast we can do this. The challenging thing is that the smaller objects that we’ve been talking about, the decameter ones, they’re really hard to detect from the ground. They’re just so small, and so that’s why we really need to use space-based facilities like JWST to help keep our planet safe. JWST is just incomparable, really, for detecting these very small, faint objects. A lot of our work at the moment at MIT is trying to understand is how do we build that entire pipeline ­— from detection to risk assessment to mitigation — under one roof to make it as efficient as possible. And I think this is a really MIT-type of problem to solve. There’s not many places that have the same range of experts in astronomy and engineering and technology to really tackle this properly. It’s really exciting that MIT hosts all these sorts of experts that we’re bringing together to solve this problem and keep our planet safer.Cambioni: There is going to be what I like to call an asteroid revolution coming up because in addition to JWST’s observational capabilities, there is a new observatory in Chile called the Vera Rubin Observatory that could increase the detection of known small objects in space by a factor of 10. The most important thing to keep in mind, though, is that this observatory will detect the objects but may lose a lot of them. This is where a part of our work is coming in, to basically follow that object and map it as soon as possible. Additionally, Vera Rubin only looks at the reflected light, and it doesn’t get a precise estimate of an asteroid’s size. This gap between detection and characterization is a fundamental problem of asteroid science, between how many objects we discover and how fast we can characterize them. At MIT, we are using our in-house capabilities to help characterize these objects. That includes the MIT Wallace Observatory and the MIT Haystack Observatory.Q: What role can MIT play in this new era of planetary defense?De Wit: The reality is that, given the occurrence rate of these smaller asteroids and the new observational capabilities now coming online — from the Rubin Observatory to space-based facilities like JWST — we expect that within the next decade we will identify a handful of decameter-scale objects whose trajectories place them on course to impact the Earth-Moon system within this century. At that point, society will face a very practical question: whether, and how, to respond. Because these are much smaller objects than the dinosaur-killing asteroids, the types of mitigation strategies that we may envision are different. This is also where I think MIT might have an important role to play in the development, design, and potentially even construction of cost-effective, rapid-response asteroid-mitigation strategies. To help organize that effort, we have begun bringing together researchers across the Institute through the Planetary Defense at MIT project, working closely with colleagues on the engineering side.Teague: What I’m particularly excited about is the way we’ve managed to engage students at MIT in this research as well. We’ve really focused on the impactful research and the way we’re bridging departments and labs within MIT, and this has been a fantastic way to engage students with practical astronomy and research. Saverio has run an IAP [Independent Activities Period] course, and we’re also running a student observing lab with the Wallace Observatory, where we hire a cohort of students every semester, and they’re taught how to use these observatories remotely. They take the data, do the analysis, and this semester, we’ve got on the order of 10 undergraduate students that are going to be working throughout the semester to take these observations and help us build this observation pipeline.It’s great that here at MIT we’re not only pushing the forefront of the research, but we’re also training the next generation of astronomers that is going to come in and carry this project through and into the future.