FAQ: Your asteroid questions answered!

Thursday, July 01, 2021 


After every Neighborhood Lecturewe have a question and answer session with the presenting scientist, and this month's Asteroid Day lecture didn't disappoint!

On June 30, 2021, Larry Nittler took us back in time to the early days of our Solar System through the lens of asteroid research. As always, our Neighborhood Lecture guests asked great questions, but we couldn't get to all of them live. Below, Nittler answers more of your asteroid questions. 


 

I get how the dust would collapse and form stars and planets but why does the disc rotate?

It is due to the Physics law of Conservation of Angular Momentum. The gas in the cloud was moving a bit when it started to collapse which led to increased spinning as it got smaller (like a figure skater bringing in their arms and spinning faster). The detailed physics calculations indicate when this happens you get a rotating disk.

We call it the asteroid belt. What is the probability that it was once a planet that was blasted to smithers by a collision by another body (from within or outside the solar system? 

Many asteroids are indeed pieces of larger bodies that got smashed up by collisions. However, it is not possible that most asteroids were once part of a larger planet because their compositions indicate that they are not differentiated. That is, their compositions are similar to the bulk Sun but if they were from a smashed-up planet, this would not be the case. Planets are differentiated into a metal core and an iron-poor mantle and crust, and only a small fraction of asteroids have compositions that match.

How big is the asteroid Ceres?

It's almost 1000 km across— the largest asteroid (now designated a dwarf planet.)

How can an asteroid be named after me? Or something I like?

Discoverers have naming rights. Find somebody who discovers new asteroids and suggest names. 

The objects that have been seen at night over the Pacific and the western coast, could they be asteroids?

When asteroids pass through the atmosphere, they get very hot, and hence very bright. They can be seen as a bright light in the sky for many seconds, but they travel in a straight line. They can break up on entry, however, making a series of bright lights that track across the sky in slightly different directions. They often are identified as UFOs, but they cannot stop, or turn, or do some of the other things that the objects you mention are alleged to have done.

What do we know about Ryugu's internal structure—is it possible that it has much more fine-grained material inside?

Yes, it is likely that the high porosity has allowed for fine-grained material to sink below the surface.

Why do Ryugu and Bennu have a similar shape?

It turns out that computer modeling of the physics of asteroid breakup and re-accretion leads naturally to such a shape.

Is the dark sample similar to our Earth’s obsidian?

No, primitive materials like carbonaceous chondrites do not contain obsidian, which is a volcanic material (there are no volcanoes on C-asteroids)

I understand that the 'boulders' on Bennu are very soft. Is that true?

The rocks on both asteroids appear to be highly porous which means they may be soft and crumbly, but we won't know until we look at the samples in detail. Probably a range in how hard or soft they really are!

What if Ryugu does not belong to any known class of carbonaceous chondrites? What will that mean?

It would mean that meteorites do not sample the full range of asteroids in the Solar System.

How were the extremely dark asteroids detected?

Although they are very dark, the Sun is very bright, so 2% reflected light is still enough to detect. However, it helps that they are Near-Earth objects; it's much harder to detect such small, dark things farther from the Sun. The brightness of the Sun decreases with the square of the distance, so Ryugu at 4 AU would see 16 times less sunlight and we would see much less of the reflected light.

How does the variation of color of carbonaceous chondrites or C-type asteroids occur? Is it related to alteration by water or heat? Why is Ryugu black?

We don't yet know! It may be that Ryugu has a higher amount of carbon—which is very dark—than other asteroids. Color variations reflect different minerals.

When you were a kid and first became interested in space stuff, did you in your wildest dreams imagine you’d be part of missions like this? And was there someone who inspired you to imagine bigger than you thought possible?

I certainly dreamed of being a space scientist, but not specifically about a mission like this! I got excited first at age 3 when I saw Apollo 17 return on TV, but much more so when I saw pictures of Mars and Jupiter (from Viking and Voyager missions) in National Geographic a few years later. Carl Sagan and his Cosmos TV series had an enormous impact on me.

Are the spacecraft preprogrammed to fly towards the asteroid that they are trying to study, and how do people control its trajectory during its flight? Is it necessary to communicate with it, or does it just fly and then return all on its own? 

Space is really really big, so it is mandatory to have interactive control of spacecraft and be able to fire the engines occasionally to fix the trajectory. Hayabusa2 traveled billions of kilometers to rendezvous with an 800-m object. This required fine-tuning of the orbit throughout. Constant interaction with spacecraft also allows for updating software for the spacecraft and instruments as needed.

If we cool Sun to make a solid phase, what kind of meteorite/asteroid will the Sun most resemble?

I would say a comet with a very large H/He atmosphere. I do not think there is solid H anywhere (except in water ice which is why I answered with comets, but the H/O ratio is so high that there will still be a lot of H even if all the O is in ice and rock

When 96 % of sunlight is absorbed by the asteroid, what happens to the absorbed light, and does it make chemical changes?

It heats it up! The surface is in fact quite warm (up to almost 200 degrees F!). This is still below the temperature required to make major chemical changes, but it may affect organics and clay minerals. This is something we will be looking for in the samples.

Will samples be returned from Psyche?

Nope, it's just an orbiter.

Did the minute contact the spacecraft had with the asteroids change their orbits in any small way?

By the laws of physics, yes, but almost certainly in a completely negligible way.

Is it possible to actually do a core sample on another mission?

Anything is possible if you spend enough money!

Given that the asteroid belt is not static, how is it changing and evolving?

This is something that solar system dynamicists study and it's very complex. Every asteroid sees the gravitational effects of the Sun and Jupiter. This tugging can cause their orbits to change. This is why there are collisions in the belt and why meteorites get thrown into the inner solar system.


If you want to learn more about asteroid research at the Earth and Planets Laboratory, read, "Why Carnegie scientists are excited to study the asteroid samples from Ryugu." 



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