Most potentially hazardous asteroids remain unidentified. NEO surveyor could change that, but only if it’s funded, and soon.
In all the world, there are few things more immediately dangerous to humanity than the potential for a large, massive object, like an asteroid or a comet, to collide with our planet. While our imaginations might immediately go to the devastating event 65 million years ago that led to our planet’s most recent mass extinction, the unsettling truth is that similar, smaller, but only slightly-less-catastrophic planetary strikes happen far more frequently. Unless we know what’s out there and can quantify the danger that this population of objects pose to us, we’re simply betting our continued existence on pure luck.
The only way to remedy the situation is to look out at the greater Solar System and determine what objects are out there and what their orbits are, alerting us to any potential near-or-medium-term risks that may require a planet-saving intervention. Unfortunately, practically all of the leading efforts towards planetary protection to date have been ground-based, which is not only an extremely limiting approach to the problem, but one that’s already gotten much less efficient and effective with the recent onslaught of satellite megaconstellations polluting our night sky.
One mission, however — NASA’s NEO Surveyor — has the potential to find and characterize the majority of yet-undiscovered objects that pose a hazard to Earth. Unless we want to continue to bet the entire planet’s survival on pure luck, everything depends on us choosing to fund this mission.
A rapid impact of a large, massive object with Earth could create a catastrophe unlike any other ever experienced by humanity. The Earth itself, if struck by a large enough, energetic enough impact, would still remain intact, but regional or even global devastation would ensue. (Credit: James Thew via Adobe Stock)
Here in our Solar System, we typically think of its structure as follows:
the Sun sits at the center,
orbited by the four inner, rocky planets,
where a large, massive belt of thousands of asteroids sits out beyond the orbit of Mars,
with the giant planets, Jupiter through Neptune, orbiting beyond the asteroids,
and then, out beyond Neptune, lies the Kuiper belt and then the Oort cloud, the primary sources of the comets that occasionally pass through the Solar System.
This picture isn’t wrong, but it isn’t quite complete. These components certainly exist, but there’s even more that appears when we look at our cosmic backyard in even greater detail. In reality, there are small, icy-and-rocky bodies that orbit between the asteroid and Kuiper belts — the centaurs of the Solar System — as well as a number of asteroids that have left the asteroid belt entirely, now orbiting the Sun along with the inner planets. Of this latter population of objects, a significant number of them come within about 5 million miles (8 million kilometers) of Earth’s orbits, and these collectively are the potentially hazardous asteroids we’re so worried about.
The bright star Albireo, a prominent and colorful double star system that’s a member of the Summer Triangle, was imaged on December 26, 2019. During 10 exposures lasting 150 seconds each, a train of Starlink satellites passed through that same region of sky. While this streaking effect has significant implications for professional an amateur astronomy alike, it’s the science of planetary protection that suffers the greatest losses, particularly from satellite impacts on ground-based observatories. (Credit: Rafael Schmall)
While it’s true that we’ve found many of these objects, the unfortunate reality is that we know we still have yet to identify the overwhelming majority of them. There are three main reasons why this is the case.
Asteroids tend to be small, faint, and fast-moving relative to Earth. Unless your telescope is capable of imaging the same asteroid many times over a multi-week timespan — which most of our asteroid-identifying telescopes, such as Pan-STARRS, are incapable of for most asteroids due to their small size — we won’t have enough data to determine its orbit, and hence even though we might know it exists, we cannot hope to find it again.
Most of the ground-based efforts to find these objects, which encompasses almost all of our planetary defense efforts to date, now have to contend with an extraordinarily large (and growing) number of confounding factors: the growing set of megaconstellations of satellites. The Large Synoptic Survey Telescope at the Vera Rubin Observatory should have been a tremendous upgrade to our planetary defense efforts, but given the recent advent of thousands of bright new satellites in low-Earth orbit, a new form of light pollution is plaguing these key observations, particularly during the hours surrounding dusk and dawn: the best time for finding these near-Earth asteroids.
But even beyond the technical limitations of ground-based astronomy, there’s the problem that asteroids fall into different groups based on their orbits: Amors, which orbit exterior to Earth, Apollos, which mostly orbit exterior to Earth but do cross our planet’s orbit, Atens, which cross Earth’s orbit but spend most of their time interior to it, and Atiras, which fully orbit interior to Earth. Ground-based observatories are good at finding Amors and are somewhat good at finding Apollos, but are lousy at finding Atens and even worse at finding Atiras.
If we want to find and characterize most of the potentially hazardous asteroids out there, we need to do it from space.
Since it was first proposed back in 2006, this has been the major science goal of NASA’s NEO Surveyor mission. The mission would put a wide-field infrared space telescope into orbit, where it would have only one major science goal: to identify and determine the orbits of every potentially hazardous asteroid close to Earth...
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