On Valentine's Day in 1990, the Voyager spacecraft, out beyond the orbit of Neptune, turned back and looked towards the inner solar system and took this portrait of the Earth from the edge of the solar system. And Carl Sagan, the astronomer, challenged us at the time to consider this pale blue dot.
Let's see, and the last team that I'm want to mention here, David Kring from the Lunar and Planetary Institute in Houston. They study the inner solar system impact processes. And you'll see a similarity in themes in all the things I'm saying here.
And we can think of those as kind of the leftover of building rubble from making the planet. So they formed in the inner solar system , much closer to the sun, just as the rocky planets did, like Earth and Mercury, Venus and Mars. And it was just those bits and pieces of planet that didn't get made into a planet.
I gather what it's about is they sent basically miners to space. But it was traveling into the inner solar system .
And that's what we did with Giotto in 1986. As Halley swung through the inner solar system , we were able to get Giotto to fly by at 68 kilometers a second. And we had just minutes of that encounter, the first time that a comet was seen close up, the comet nucleus.
And then there was a huge reorganization of the solar system after the large planets formed. And some of these comets kind of got thrown into the inner solar system and got trapped in the asteroid belt. So we actually find that they're kind of of comets, but they are asteroids.
And comets could be a very important vector for that, because they lock up ice and dust in the outer solar system. And those objects and then come into the inner solar system through perturbations and impact on the planets. You need about 100 million comets to get the water we have on the Earth.
kind of like huge and close together, yeah, but it's really kind of-- They're quite scattered out, and that's a good thing, otherwise they would collide more often and we would have more issues in the inner solar system with potentially being hit by one. So actually it's a good thing that they're nicely far part.
I gather what it's about is they sent basically miners to space. We're still trying to understand how we get hot material from the inner solar system out to the comet forming region to form a comet that then is
Let's suppose the next best thing you want to do. You want to find one of those objects that's coming into the inner solar system . Those of you who remember your physics would know that if you have something that's in as eccentric of an orbit as that,
But there's rain that appears. But in the meantime, rearranging the inner solar system is kind of a neat thing.
And this is literally a cloud around the whole sun. So what happens is, is when one of these comets decides to come into the inner solar system , they can come in from all random angles. They're not going to be coming along that plane.
Now Halley lives out deep in the solar system, way out beyond the giant planets. And it comes in every 76 years, accelerates towards the inner solar system , goes extremely fast through the middle, and back out again. And so what we could do, what we were capable of doing in 1986, was effectively do what anybody in this room--
The reason is that the surface of comets is because of these dust covering and these carbon-bearing molecules is not really the primordial material anymore. It's being processed. Every time a comet's come through the inner solar system , it's being frazzled, fried. Think of it as a baked Alaska.
But there's rain that appears. But fortunately, as long as you're in the inner solar system , the efficiency of a solar system per unit weight
if our solar system had a planet just like the one around 51 Pegasai, where would we put it on on this map of the solar system? Well, we couldn't put it on this diagram. We have to zoom way in here to the inner solar system . Okay, so now we're looking at Mercury and Venus, Earth, and Mars. And the planet around 51 Pegasi would be something like this,
It's so far away. And we always talk about Oort Cloud comets and, neato, we have what we call long period comets, which are these comets that come into the inner solar system and orbit the sun and they have to have orbits of more than 200 years.
So we get to-- after that, we turn this the spacecraft off, spin it up, and pray. But it's the surface structures which have everybody amazed, because this comet actually has not been in the inner solar system for very many years.