Devil-sAdvocate t1_it8ha09 wrote on October 21, 2022 at 6:20 PM

Reply to comment by danielravennest in As many as a fifth of all asteroids in the asteroid belt may have been formed out on the fringes of the solar system. Findings suggest that both Ryugu and the CI chondrites originate from the same region of space, and could even have shared the same parent body. by marketrent

Nice, but the subject I was questioning was if 'the asteroid belt' is also a great protector.

dialectrical t1_it8hrkr wrote on October 21, 2022 at 6:23 PM

Well it’s great belt for ass whooping

danielravennest t1_itbulsb wrote on October 22, 2022 at 1:25 PM

The asteroid belt has minimal mass (3% of our Moon). So it doesn't affect its own members much, or stop anything else from passing through.

Jupiter is 850,000 times more massive than the entire belt, so it strongly affects their orbits. For example, any asteroid that has a simple ratio to Jupiter's orbit gets pulled in the same direction every time it is closest. This pulls it out of that orbit, creating gaps in the belt. Conversely other asteroids are trapped in resonant orbits to Jupiter - the Trojans and Hildas.

Devil-sAdvocate t1_itcugbt wrote on October 22, 2022 at 5:47 PM

So the main belt is not a protector of earth but a danger as the orbits of belt asteroids can be changed by Jupiter's massive gravity – and by occasional close encounters with Mars or other objects. These encounters can knock asteroids out of the main belt, and hurl them into space in all directions across the orbits of the other planets- like earth.

https://redwoodriverresort.com/parkmap

https://redwoodriverresort.com/cabins

danielravennest t1_itfzxq7 wrote on October 23, 2022 at 11:06 AM

Exactly. Japan sent a probe to the asteroid Ryugu and brought back samples. The samples indicate its material formed in the outer Solar System. but now it's orbit crosses Earth's (that's why the picked it to visit).

More generally, there are 30,000 known asteroids whose orbits come closer than 1.3 times the Earth's distance to the Sun. That compares to over a million other asteroids. These "near Earth asteroids)" have an orbit half-life of 10 million years, which is very short compared to the age of the Solar System.

So these asteroids need to be constantly resupplied, otherwise there would be none left. The giant planets, which is mostly Jupiter since it is heavier than everything else combined, are the main cause of orbit changes.

The near Earth asteroids are the ones most likely to hit Earth, which is why NASA has a search program for them, and why they just tested changing an orbit by hitting it. What we have going for us is space is really empty. Earth only takes up one part in 500 million of our orbital region. So the chance of any given random rock hitting us is low. On the other hand, there are many rocks. Dust and sand-sized ones hit us every day. That's what meteors in the night sky are.

thejoeymonster t1_itnaai0 wrote on October 24, 2022 at 10:07 PM

Earth's orbit is 500million times it's diameter?

danielravennest t1_itpxg9q wrote on October 25, 2022 at 1:26 PM

No. Our orbit is 23,455 times the size of the Earth. But there is a second dimension, above and below our orbit.

This plot shows the size of asteroid orbits relative to ours on the horizontal scale, and the tilt in degrees relative to the Earth's orbit. You can see the tilts go up to 30-40 degrees.

Any tilt above zero means when they cross our orbit's distance, they can be crossing above or below where the Earth will pass. They can only hit us if they cross our distance exactly on our path, and the Earth also happens to be at that point in our orbit at the same time.