I work on the NASA NEO Surveyor project (and have helped out a lot on the WISE/NEOWISE mission, which found a lot of asteroids). I create and run simulations of asteroid detections, which ends up being mostly orbit calculations.
In the next few years the rate of detections of these sort of objects are going to go way up, NEO Surveyor and the Vera Rubin LSST telescopes are going to take our current knowledge of the solar system from about 1.4 million asteroids to approximately 10x that. It is somewhat difficult to estimate how many we will see, since the size distribution follows a power law, and small changes in our estimates of the slope can be huge changes the number which exist.
There are most likely hundreds of thousands to millions of a few meter sized asteroids flying around the inner solar system.
I recommend figure 12 to get a sense of how far we can see at any given moment.
The definition which is commonly used as "hazardous" is about a 140m asteroid, which would cause a significantly bad day regionally, but not end civilization. That being said, 50m is still a very very bad day.
These meter-ish size ones usually just make a pretty fireball.
For anyone else curious who wants some tangible sense of the dangers, the Tunguska impactor is estimated to have been 50-60m in diameter [1]. The impactor that created the Barringer Crater in Arizona is estimated to have been about the same size [2].
Regarding a 100m asteroid impact:
> The pressure blast would destroy buildings up to 9 miles (15 km) from ground zero, and windows would shatter more than 60 miles away (100 km). To make matters worse, as the partially burned rock hit the ground, it would trigger seismic tremors that would spread through the planet's crust, carrying the destruction further away from the epicenter. The debris ejected into the air by the force of the impact would rain back on the ground miles away from the impact site, and the finer dust and dirt would remain hanging in the air, spreading with the wind across large distances.[3]
I can imagine a 140m asteroid causing a very, very bad day indeed for a region.
Not an expert, just curious and I can type stuff into a search engine.
I wonder, could an asteroid be traveling at a relative-to-Earth speed of very slowly, so that the impact most like just "setting down" on Earth rather than slamming into Earth?
There is minimum amount of energy from falling down Earth’s gravity well. Earth escape velocity is 11 km/s. A big chunk of asteroid energy comes from Earth’s gravity.
On the other hand, the orbital speed of Low Earth Orbit is 8km/s. Thus, with regard to asteroid redirection missions, we'd need 'only' about 3-4km/s of Δv to prevent this 'gently setting down' asteroid from hitting the Earth by capturing it into orbit.
Definitely into science fiction territory here considering that DART resulted in a Δv measured in centimetres per second, but I'm still rather tickled by the idea of collecting a new moon for ourselves :)
If we don't need to capture it to orbit, but just avoid hitting the Earth, centimeters might be enough. The trick is to be able to do it way in advance.
Besides, why LEO? Even GSO is 11 times closer than the Moon.
You're quite right - attaining GSO would indeed require only another 3 or 4km/s. But it does seem a little unfair to put it in GSO; we'd surely want people in both hemispheres to get a chance to gawk at our new satellite!
I recently decided that I wanted to learn more about your field, so I set up a jupyter notebook and was perusing the available python libraries and I found this one[0] however it is apparently unmaintained.
Can you suggest any beginner tools or resources for a layman to learn more about your field? I've taken an intro orbital mechanics course, solar system geology course and one on exoplanet detection and I'd like to keep the kinds of skills that I got from those courses fresh in my brain.
I am in the rather lengthy process of open sourcing a library for orbit propagation, but the previous art which is somewhat modern is the python rebound package. It's original design intent was for asteroid collision simulations, but it has been generalized a lot since then.
Most of the state of the art in the field is algorithms from the 60s/70s, the classic software which many people use are packages like Mercury, written in either fortran or C++.
These factors are why I am attempting to release my code to the (small) community.
How do the algorithms from something like Dan Boulet's "Methods of Orbit Determination" hold up to modern methods? I have the book, never actually did anything with it though, but have recently been thinking about giving it a try.
There are sort of two major camps in the field, the astronomers and the people who fly satellites. Having the thing you are measuring able to talk to you and get doppler measurements of its velocity is invaluable for orbit determination, so the modern techniques for the satellite group have probably continued to advance. Unfortunately on my side of the fence, rocks usually dont talk back and we have less information available for fitting. For a vast majority of the time all we get for asteroids are visible observations, which is very limited geometric information. The algorithms here have not advanced a whole lot for a looong time, Gauss famously developed the first optimization technique to find Ceres. The field still regularly uses "Gauss's Method" for orbit determination. There have been a few small improvements to numerical integrators, but the field as a whole tends to use the "tried and true" methods of the past. I had to go on ebay and get a bunch of texts from the 60s-80s as they are often the best, even now. The field is very very tiny, think maybe dozens to hundreds in the whole world.
There are most likely hundreds of thousands to millions of a few meter sized asteroids flying around the inner solar system.
I did a large chunk of the numerical analysis in this paper: https://arxiv.org/pdf/2310.12918
I recommend figure 12 to get a sense of how far we can see at any given moment.
The definition which is commonly used as "hazardous" is about a 140m asteroid, which would cause a significantly bad day regionally, but not end civilization. That being said, 50m is still a very very bad day.
These meter-ish size ones usually just make a pretty fireball.
Some various links to data about this impact:
https://cneos.jpl.nasa.gov/sentry/details.html#?des=2024%20R...
https://minorplanetcenter.net/mpec/K24/K24R68.html