Starship Asterisk*

Until then we can at least look back onto what we have done with a new extended version of Erik Wernquist's "New Horizons".

It is premature to state the surface features of Pluto have an estimated age of 100 million years or so based on the apparent absence of craters. This is our first close observation of an object as far out as Pluto, and the first observation of an object that orbits out-of-plane to the ecliptic. Our observations of cratered celestial bodies are of inner solar system objects or moons orbiting gas giants - all well within the strong gravitational fields of the Sun or gas giants that suck in debris and orbiting in the ecliptic plane. Debris thrown into the outer solar system by the gas giants, as suggested, will only achieve highly elliptical orbits and will return to the inner solar system, where there will eventually be impacts. To remain in the outer solar system, an additional impulse is required, additional velocity, to achieve a higher orbit. This is basic orbital mechanics. There simply isn't much debris at the distances of Pluto's orbit, and since most of the debris lies in the ecliptic, then Pluto spends most of its time outside of the region for the highest probability of impacts. It is therefore easy to assume that the probability of impacts on Pluto's surface is an order of magnitude less than for all other objects we've observed prior, and it is safe to assume it is far less than that. In all likelihood, the surface of Pluto is little changed since the formation of the solar system.

Scabulus wrote:It is therefore easy to assume that the probability of impacts on Pluto's surface is an order of magnitude less than for all other objects we've observed prior, and it is safe to assume it is far less than that.

No, such an assumption isn't safe at all. We have good models describing impact rates throughout the Solar System. Pluto probably has a young surface. That is the most reasonable assumption to make at this time.

geckzilla wrote:Yes, gosh darn it, as long as 'Murica is the one sending out the probes, we're going to use miles.

For some reason, I imagine you saying this in a southern accent frm somewhere like Nashville?!

That area to the upper left in the photo reminds us of the photos we have seen of Antarctica, where the mountains poke up through the ice fields and appear to be mountain-islands. We can't see any evidence of moraines that may indicate movement but that could be a resolution problem.

Otherwise, given that there are only very structures that could be craters; and that there is evidence of cratering on a previous photo; there appears to be some active process in the works. It appears as though Pluto does not get close enough to either Uranus or Neptune to cause any heating from tidal/gravitational forces. So there has to be some other process going on there. Is there any evidence of internal heating or radiation from Pluto? Or anything to indicate massive planet-buster impacts that could result in mass melting of the surface? If planet-buster impacts were the cause, wouldn't there be a lot of debris in orbit and evidence of secondary impacts?

Could it be that the surface is frozen solids when farther from the sun and then melt when closer in; causing resurfacing with each freeze-thaw cycle? If there was an active weather pattern causing erosion, shouldn't we have seen evidence (clouds, river basins, outflow patterns) by now?

starsurfer wrote:

geckzilla wrote:Yes, gosh darn it, as long as 'Murica is the one sending out the probes, we're going to use miles.

For some reason, I imagine you saying this in a southern accent frm somewhere like Nashville?!

Nope, pure okie!

bystander wrote:

starsurfer wrote:

geckzilla wrote:Yes, gosh darn it, as long as 'Murica is the one sending out the probes, we're going to use miles.

For some reason, I imagine you saying this in a southern accent frm somewhere like Nashville?!

Nope, pure okie!

I should think that there would be a little New Yawk accent mixed in by now.

I can say it with southern accent or with generic, non-special American that I'm not sure what to call it. I wouldn't have used gosh-darn-it with a southern accent though. They're more of a dang-it people. Never picked up the Brooklyn or Italian-American accents from NY.

Chris Peterson wrote:

Scabulus wrote:It is therefore easy to assume that the probability of impacts on Pluto's surface is an order of magnitude less than for all other objects we've observed prior, and it is safe to assume it is far less than that.

No, such an assumption isn't safe at all. We have good models describing impact rates throughout the Solar System. Pluto probably has a young surface. That is the most reasonable assumption to make at this time.

It is very interesting that the surface of Pluto is so young. I'm looking forward to what the scientists will be saying as to the reason(s) for it.

Ann

Ann wrote:It is very interesting that the surface of Pluto is so young. I'm looking forward to what the scientists will be saying as to the reason(s) for it.

Yes. It's an interesting planet with some unexpected properties (to the extent that we might have any expectations). These data are going to be providing rich evidence for lots of theories for a long time to come.

It's a good time to be alive.

Well, while exciting to the max, a little disappointing that at least Charon wasn't Rama. Perhaps when New Horizon visit the next Kuiper Belt object....
Out in these realms even Hollywood is beat out by sifi (as always). Clarke's award-winning novel Rendezvous with Rama (1972) was optioned for filmmaking decades ago, but this motion picture is in "development hell" as of 2015.

geckzilla wrote:I can say it with southern accent or with generic, non-special American that I'm not sure what to call it. I wouldn't have used gosh-darn-it with a southern accent though. They're more of a dang-it people. Never picked up the Brooklyn or Italian-American accents from NY.

Good choice Geck.

A "Gosh"zilla wouldn't conjure nearly enoug bite whatever the accent.

minkfarms wrote:Well, while exciting to the max, a little disappointing that at least Charon wasn't Rama. Perhaps when New Horizon visit the next Kuiper Belt object....
Out in these realms even Hollywood is beat out by sifi (as always). Clarke's award-winning novel Rendezvous with Rama (1972) was optioned for filmmaking decades ago, but this motion picture is in "development hell" as of 2015.

Nah. Rama came in on an hyperbolic orbit around the Sun. if Charon had been Rama it would have been close to Earth by now.
And with the current sorry state of our space program we wouldn't be able to rendezvous with it anyway.

Chris Peterson wrote:

APOD Robot wrote:Suggesting surprising geological activity, they are also likely young with an estimated age of 100 million years or so based on the apparent absence of craters.

Actually, I think the estimate is for a maximum age of 100 million years, with no bounds yet on how much younger the surface might be (at least until some craters are observed).

Actually, I was thinking the opposite. The age might be greater than that. My reasoning goes like this:

1) The above statement presumes that the crater creation rate would be the same across the solar system. Is this a good assumption?
2) My understanding is that the craters formed on the inner planets were formed from asteroids, comets and other debris that were displaced from their orbits by the gas giants, either in their original orbits or as the gas giants migrated to other orbits. Alternatively passing stars might also disturb objects in the Ort cloud sending them into the inner solar system
3) Displaced asteroids and comets can generally get displaced two ways -- inwards or outwards. We'll ignore those objects that get displaced off of the plane of the planets' orbits.
3a) Inwards: A percentage of asteroids and comets displaced inwards will strike an inner planet or other object creating a crater. As things fall inwards towards the sun, the probability of hitting something would increase. This is because a given arc of orbit will cover less space the closer you get to the sun. To put it differently, if asteroids and comets fall inward in a random distribution, would more of them strike Mercury than Mars for the simple reason that the probability of the falling object and Mars being in the same place and time would be much smaller than in the probability of Mercury and the object? A different way of visualizing it (forgive me, I'm struggling a bit to explain my concept) is that if any portion of Mercury's orbit has equal probability of having a piece of debris in it, (and the same applies to Mars), than all of the space debris falling into Mercury's orbit will be spread out over an area only 27% as large as Mars's, so all other things being equal, Mercury might have ~3x the craters of Mars.
3b) Looking in the other direction, debris scattered outward would be spread over a larger area, and Pluto is a fairly small object, so the probability of it hitting one of these objects would be quite a bit less than the probability of one of the inner planets being hit. In addition to the area covered by Pluto's orbit being quite a bit larger, Pluto is also a fairly small object, the chances of a piece of debris and Pluto being in the same place and time would be quite a bit less.

Given this logic, the we might encounter fewer and fewer craters on objects the further out that you go, to the point were Kuiper belt objects may only have craters on them from random collisions with other Kuiper belt objects, even though the surfaces might be very old and undisturbed.

Does this sound reasonable?

jluetjen wrote:

Chris Peterson wrote:

APOD Robot wrote:Suggesting surprising geological activity, they are also likely young with an estimated age of 100 million years or so based on the apparent absence of craters.

Actually, I think the estimate is for a maximum age of 100 million years, with no bounds yet on how much younger the surface might be (at least until some craters are observed).

Actually, I was thinking the opposite. The age might be greater than that. My reasoning goes like this:

1) The above statement presumes that the crater creation rate would be the same across the solar system. Is this a good assumption?
2) My understanding is that the craters formed on the inner planets were formed from asteroids, comets and other debris that were displaced from their orbits by the gas giants, either in their original orbits or as the gas giants migrated to other orbits. Alternatively passing stars might also disturb objects in the Ort cloud sending them into the inner solar system
3) Displaced asteroids and comets can generally get displaced two ways -- inwards or outwards. We'll ignore those objects that get displaced off of the plane of the planets' orbits.
3a) Inwards: A percentage of asteroids and comets displaced inwards will strike an inner planet or other object creating a crater. As things fall inwards towards the sun, the probability of hitting something would increase. This is because a given arc of orbit will cover less space the closer you get to the sun. To put it differently, if asteroids and comets fall inward in a random distribution, would more of them strike Mercury than Mars for the simple reason that the probability of the falling object and Mars being in the same place and time would be much smaller than in the probability of Mercury and the object? A different way of visualizing it (forgive me, I'm struggling a bit to explain my concept) is that if any portion of Mercury's orbit has equal probability of having a piece of debris in it, (and the same applies to Mars), than all of the space debris falling into Mercury's orbit will be spread out over an area only 27% as large as Mars's, so all other things being equal, Mercury might have ~3x the craters of Mars.
3b) Looking in the other direction, debris scattered outward would be spread over a larger area, and Pluto is a fairly small object, so the probability of it hitting one of these objects would be quite a bit less than the probability of one of the inner planets being hit. In addition to the area covered by Pluto's orbit being quite a bit larger, Pluto is also a fairly small object, the chances of a piece of debris and Pluto being in the same place and time would be quite a bit less.

Given this logic, the we might encounter fewer and fewer craters on objects the further out that you go, to the point were Kuiper belt objects may only have craters on them from random collisions with other Kuiper belt objects, even though the surfaces might be very old and undisturbed.

Does this sound reasonable?

The thing that makes your idea seem less reasonable to me, is that an object on a highly eccentric orbit, passing through the inner solar system, spends only a small fraction of its time in the inner solar system. Most of the time it lurks in the outer reaches.

jluetjen wrote:

Chris Peterson wrote:

APOD Robot wrote:Suggesting surprising geological activity, they are also likely young with an estimated age of 100 million years or so based on the apparent absence of craters.

Actually, I think the estimate is for a maximum age of 100 million years, with no bounds yet on how much younger the surface might be (at least until some craters are observed).

Actually, I was thinking the opposite. The age might be greater than that. My reasoning goes like this:

1) The above statement presumes that the crater creation rate would be the same across the solar system. Is this a good assumption?

The assumption about uniform crater creation rate is false, as is your assumption that this applies to the above statement.

2) My understanding is that the craters formed on the inner planets were formed from asteroids, comets and other debris that were displaced from their orbits by the gas giants, either in their original orbits or as the gas giants migrated to other orbits. Alternatively passing stars might also disturb objects in the Ort cloud sending them into the inner solar system

Generally, yes, but why do you speak in the past tense? This is an ongoing process, and it isn't limited to the inner system. Plenty of material is jettisoned into orbits that extend well beyond Pluto, as well.

3) Displaced asteroids and comets can generally get displaced two ways -- inwards or outwards. We'll ignore those objects that get displaced off of the plane of the planets' orbits.

Although there is a concentration of material near the ecliptic plane (or the invariable plane- for our purposes they are essentially the same), there is also a great deal of material orbiting at high inclinations. This material also contributes to collisions.

3a) Inwards: A percentage of asteroids and comets displaced inwards will strike an inner planet or other object creating a crater. As things fall inwards towards the sun, the probability of hitting something would increase. This is because a given arc of orbit will cover less space the closer you get to the sun. To put it differently, if asteroids and comets fall inward in a random distribution, would more of them strike Mercury than Mars for the simple reason that the probability of the falling object and Mars being in the same place and time would be much smaller than in the probability of Mercury and the object? A different way of visualizing it (forgive me, I'm struggling a bit to explain my concept) is that if any portion of Mercury's orbit has equal probability of having a piece of debris in it, (and the same applies to Mars), than all of the space debris falling into Mercury's orbit will be spread out over an area only 27% as large as Mars's, so all other things being equal, Mercury might have ~3x the craters of Mars.
3b) Looking in the other direction, debris scattered outward would be spread over a larger area, and Pluto is a fairly small object, so the probability of it hitting one of these objects would be quite a bit less than the probability of one of the inner planets being hit. In addition to the area covered by Pluto's orbit being quite a bit larger, Pluto is also a fairly small object, the chances of a piece of debris and Pluto being in the same place and time would be quite a bit less.

Yes. But this is well understood, and accounted for in using crater density to estimate surface age.

Given this logic, the we might encounter fewer and fewer craters on objects the further out that you go, to the point were Kuiper belt objects may only have craters on them from random collisions with other Kuiper belt objects, even though the surfaces might be very old and undisturbed.

KBOs still lie inside the Oort cloud, and will be subject to collisions over millions of years. I think the estimate of 100 million years for the maximum surface age is based on a reasonable model of cratering rate for a body the size of Pluto, in Pluto's orbit. The same formula isn't used here as would be used with, for example, Mars.

Nitpicker wrote:

jluetjen wrote: Actually, I was thinking the opposite. The age might be greater than that. My reasoning goes like this:

1) The above statement presumes that the crater creation rate would be the same across the solar system. Is this a good assumption?
2) My understanding is that the craters formed on the inner planets were formed from asteroids, comets and other debris that were displaced from their orbits by the gas giants, either in their original orbits or as the gas giants migrated to other orbits. Alternatively passing stars might also disturb objects in the Ort cloud sending them into the inner solar system
3) Displaced asteroids and comets can generally get displaced two ways -- inwards or outwards. We'll ignore those objects that get displaced off of the plane of the planets' orbits.
3a) Inwards: A percentage of asteroids and comets displaced inwards will strike an inner planet or other object creating a crater. As things fall inwards towards the sun, the probability of hitting something would increase. This is because a given arc of orbit will cover less space the closer you get to the sun. To put it differently, if asteroids and comets fall inward in a random distribution, would more of them strike Mercury than Mars for the simple reason that the probability of the falling object and Mars being in the same place and time would be much smaller than in the probability of Mercury and the object? A different way of visualizing it (forgive me, I'm struggling a bit to explain my concept) is that if any portion of Mercury's orbit has equal probability of having a piece of debris in it, (and the same applies to Mars), than all of the space debris falling into Mercury's orbit will be spread out over an area only 27% as large as Mars's, so all other things being equal, Mercury might have ~3x the craters of Mars.
3b) Looking in the other direction, debris scattered outward would be spread over a larger area, and Pluto is a fairly small object, so the probability of it hitting one of these objects would be quite a bit less than the probability of one of the inner planets being hit. In addition to the area covered by Pluto's orbit being quite a bit larger, Pluto is also a fairly small object, the chances of a piece of debris and Pluto being in the same place and time would be quite a bit less.

Given this logic, the we might encounter fewer and fewer craters on objects the further out that you go, to the point were Kuiper belt objects may only have craters on them from random collisions with other Kuiper belt objects, even though the surfaces might be very old and undisturbed.

Does this sound reasonable?

The thing that makes your idea seem less reasonable to me, is that an object on a highly eccentric orbit, passing through the inner solar system, spends only a small fraction of its time in the inner solar system. Most of the time it lurks in the outer reaches.

Ok, that would suggest even fewer craters than.

jluetjen wrote:Ok, that would suggest even fewer craters than.

Not to me, it doesn't. (Besides, I am sure the best current models for the varying rate of cratering throughout the solar system, consider many more factors.)

Wow, four days of self imposed tv blackout and no internet access and I come back ans see this..DOUBLE WOW

Can someone tell me where does the light come from to illuminate the surface of Pluto when the Sun is just another star in the sky so very far away? I have enjoyed APOD for decades and love the magnificent photography. Thank you.

Ironsides wrote:Can someone tell me where does the light come from to illuminate the surface of Pluto when the Sun is just another star in the sky so very far away? I have enjoyed APOD for decades and love the magnificent photography. Thank you.

Um, it comes from the Sun. It is brighter than you think on Pluto. You can experience it yourself by following the instructions on the following website:
http://solarsystem.nasa.gov/plutotime/
... and then going outside at the allotted time.

I read somewhere that sunlight at Pluto was similar to that of a 40 watt lightbulb if this is the case, just light up a room with a 40 watt light and see how bright it is or go outside 10 minutes after sundown

go here: http://eyes.jpl.nasa.gov/eyes-on-pluto.html
Download app... move time to around July 14, then turn around and look at the Sun!
Brighter and larger than I would have thought...

Nitpicker wrote:

Ironsides wrote:Can someone tell me where does the light come from to illuminate the surface of Pluto when the Sun is just another star in the sky so very far away? I have enjoyed APOD for decades and love the magnificent photography. Thank you.

Um, it comes from the Sun. It is brighter than you think on Pluto. You can experience it yourself by following the instructions on the following website:
http://solarsystem.nasa.gov/plutotime/
... and then going outside at the allotted time.

Thank you. That was a very informative web site. When I first read a snip from NASA that our Sun was just a bright star when viewed from Pluto I thought it must be illuminated no better than a moonlit night on Earth.

Nitpicker wrote:

jluetjen wrote:Ok, that would suggest even fewer craters than.

Not to me, it doesn't. (Besides, I am sure the best current models for the varying rate of cratering throughout the solar system, consider many more factors.)

Chris Peterson and Nitpicker; Since I'm just a layman who doesn't read (nor even have access to) the specialist publications -- could you point me in the direction of a study that looks at crater distribution across the solar system. Doing some internet searches, I could find some that look at the inner planets, some that look at the moons of the giants, and many that look at a single planet while correlating with other factors like weathering and stuff, but nothing that looks at the distribution from inner planets out to the outer planets. Not to mention, Pluto may be a completely new case since it's orbit isn't on the same plane as the major planets.