ESA Rosetta to 67P/Churyumov-Gerasimenko.

[EarthlingX]

Re: Asteroid 21 Lutetia (ESA Rosetta Encounter).

Thank you Andrew for the work on images - it makes life easier and prettier

Congratulations to Rosetta team - very nice show :mrgreen:

SDC : Mysterious Asteroid Unmasked By Space Probe Flyby

By Denise Chow

SPACE.com Staff Writer

posted: 10 July 2010 02:53 pm ET



A European spacecraft zoomed by past a mysterious asteroid Saturday to take the first-ever close look at the space rock while flying more than 282 million miles from Earth.

The European Space Agency's (ESA) Rosetta space probe flew past the asteroid Lutetia, an object discovered in 1852 that appeared only as a bright speck in the sky to astronomers until today.

The first new photos of the asteroid revealed Lutetia to be a lumpy rock with a potato-like appearance. Rosetta was about 1,900 miles (3,100 km) from the asteroid at its closest approach.

 

[EarthlingX]

Re: Asteroid 21 Lutetia (ESA Rosetta Encounter).

http://www.planetary.org : Rosetta's Lutetia pictures

By Emily Lakdawalla

Jul. 10, 2010 | 22:17 PDT | Jul. 11 05:17 UTC

I saw these pictures for the first time just 10 minutes before boarding my flight back home, and forced myself to download everything I could find as quickly as possible without pausing to actually look at them. (Well, except for the Saturn one, which I knew was coming. That one I had to post without even thinking about it.) Still, even in passing, I caught sight of lovely bowl-shaped craters and Phobos-esque grooves.

Now I have time to study them, and Lutetia is certainly a world different to other asteroids that have been visited before. Here is the last image (at least of the set released this evening by ESA) in which the entire body fit within the OSIRIS field of view; there are a couple more that are higher-resolution, but bits of the edge of the disk are clipped off. The version as released was a bit saturated in the most brightly sunlit areas, so I fiddled with the levels to bring out more detail there. That fiddling did make the dark parts of the disk a bit dim. It's hard to process a picture so that you can see detail everywhere.


A full view of Lutetia from Rosetta
In a photo captured a bit less than five hours before its closest approach, Rosetta's OSIRIS camera captured a detailed view of the full globe of 21 Lutetia, the largest asteroid yet visited by a spacecraft. Credit: ESA 2010 MPS for OSIRIS Team MPS / UPD / LAM / IAA / RSSD / INTA / UPM / DASP / IDA

 

[EarthlingX]

Re: Asteroid 21 Lutetia (ESA Rosetta Encounter).

http://www.esa.int : Rosetta triumphs at asteroid Lutetia

10 July 2010


Lutetia at Closest approach

Asteroid Lutetia has been revealed as a battered world of many craters. ESA’s Rosetta mission has returned the first close-up images of the asteroid showing it is most probably a primitive survivor from the violent birth of the Solar System.

The flyby has been a spectacular success with Rosetta performing faultlessly. Closest approach took place at 18:10 CEST, at a distance of 3162 km.

The images show that Lutetia is heavily cratered, having suffered many impacts during its 4.5 billion years of existence. As Rosetta drew close, a giant bowl-shaped depression stretching across much of the asteroid rotated into view. The images confirm that Lutetia is an elongated body, with its longest side around 130km.

The images come from OSIRIS instrument, which combines a wide angle and a narrow angle camera. At closest approach, details down to a scale of 60 metres can be seen over the entire surface of Lutetia.

“I think this is a very old object. Tonight we have seen a remnant of the Solar System’s creation,” says Holger Sierks, OSIRIS principal investigator, Max Planck Institute for Solar System Research, Lindau.

 

[3488]

Re: Rosetta Mission thread

Bump, I am amalgamating threads.

 

[3488]

Mission Recaps. All are clickable thumbnails.

Ariane 5 prior to launch with Rosetta.


Rosetta Launch. Tuesday 2nd March 2004. 4:17 AM.


First Earth & Moon encounter Rosetta. Saturday 5th March 2005.


Mars Saturday 24th February 2007 from Rosetta.


Mars from the attached Philae Lander Mawrth Vallis is visible.


Second Earth & Moon encounter. Tuesday 13th November 2007.


Asteroid 2867 Šteins encounter. Friday 5th September 2008. Main belt very rare Type E asteroid, 5.9 KM by 4.0 KM, so pretty small. This for me was one of the best & most exciting parts of the mission.




Third & Final Earth encounter. Friday 13th November 2009.


Below, to me, perhaps the best part of the mission.

Large 132 KM wide Main Belt Asteroid 21 Lutetia encounter. Saturday 10th July 2010.




Andrew Brown.

 

[orionrider]

Excellent summary, thank you Andrew

 

[3488]

You are very welcome Orionrider.

It was a lot of work, but, both members newtons_laws & alpha_centauri were perfectly correct & justified asking why there was not a generic Rosetta thread.

there was, but it was old, & most of it was lost when SDC was 'depluckified' . The problem was, & still is, that Rosetta's main events are seperated by quite considerable time gaps, the gap between the Earth encounter # 3 & the Asteroid 21 Lutetia pass, was the shortest, November 2009 to July 2010 respectively!!!!

I have merged what I could find, primarily the old thread, at least that part post depluckification & the Asteroid 2867 Šteins & Asteroid 21 Lutetia threads & chucked them all together as one. Then to trawl through the older images as well as the newer 2867 Šteins, Earth encounter # 3 & 21 Lutetia ones, sort them & repost them as clickable thumbnails.

Andrew Brown.

 

[3488]

I have worked on a few more Asteroid 21 Lutetia crops from yesterday's Rosetta encounter.

Enlarged, sharpened crop of floor of central 20 KM portion of basin.

Enlarged, sharpened crop of 20 KM wide 'smoother' area, either a ghost crater likely filled with regolith or a massive landslide.

Enlarged, sharpened crop 19.5 KM area enhanced contrast of another region heavily grooved.

Enlarged, sharpened crop of a 16.5 KM area with a sharp crater with interneal striations, certainly debris sliding down the crater walls & at least one large boulder just to the outside at the 1 o'clock position.

Enlarged, sharpened, contrast enhanced crop rotated 90 degrees of a 35 KM portion of limb, rotated to look like a horizon. That lump or mountain is approx 5,000 metres tall.

There have been no further releases today, hopefully from tomorrow there will be.

Andrew Brown.

 

[alpha_centauri]

You are very welcome Orionrider.

It was a lot of work, but, both members newtons_laws & alpha_centauri were perfectly correct & justified asking why there was not a generic Rosetta thread.

there was, but it was old, & most of it was lost when SDC was 'depluckified' . The problem was, & still is, that Rosetta's main events are seperated by quite considerable time gaps, the gap between the Earth encounter # 3 & the Asteroid 21 Lutetia pass, was the shortest, November 2009 to July 2010 respectively!!!!

I have merged what I could find, primarily the old thread, at least that part post depluckification & the Asteroid 2867 Šteins & Asteroid 21 Lutetia threads & chucked them all together as one. Then to trawl through the older images as well as the newer 2867 Šteins, Earth encounter # 3 & 21 Lutetia ones, sort them & repost them as clickable thumbnails.

Andrew Brown.

Thankyou very much (sorry to be a pain! ) I think fully deserved for this exciting mission, I seriously can’t wait til it reaches C-G. The irony is I see I posted in the original thread here but forgot about it!

Yes it is a bit of a pain everything being so far apart but hopefully the analysis of the data from the latest pass and perhaps ground-based follow-ups should give a lot to chew over for perhaps another year.

There have been no further releases today, hopefully from tomorrow there will be.

Are you sure there are going to be any more releases before the September meeting? They might be tempted, now that the media rush has gone by, to sit on the other images til then.


Lastly I don’t think it’s been posted anywhere else so here’s a link to the DLR write-up (DLR was the chief agency involved with the Osiris camera) which I think has a slightly different write-up of the encounter than the rest we’ve seen.

http://www.dlr.de/en/DesktopDefault.asp ... ead-25549/

 

[newtons_laws]

3488, Thank you very much for generating this generic Rosetta thread here on this forum.
It is much appreciated.

 

[alpha_centauri]

In a similar vein to 3488’s post-encounter report perhaps it’s a good time to evaluate the “known knowns” and the “known unknowns”.

As 3488 says, Lutetia superficially looks very much like a C-type asteroid, slightly disappointingly as it would mean we still haven’t seen a true M-type up close.

Pre-flyby size estimates appear to have been pretty close and the polarisation data seems corroborated with the very large depression (impact related or something else? Curious) in one side.

But this does raise some interesting questions not least why, if the ground-based measurements prove accurate, does Lutetia appear to have such a high density? Fully twice as much as the higher density C-types known.

http://home.earthlink.net/~jimbaer1/astmass.txt

Indeed much closer to 16 Psyche, a likely pure metallic asteroid, than any of the C-types.

Is it possible that this, clearly very old, asteroid very early in its formation was a metal M-type that aggregated a large CC surface?

 

[MeteorWayne]

We'll know more about the actual density in a few days when the encounter data in analyzed. Pre encounter, we had no idea of the actual mass, volume or density. All 3 were strictly estimates based on a lot of assumtions, and since density is derived from the other two, it was exponentially estimated.

MW

 

[scottb50]

Re: Asteroid 21 Lutetia (ESA Rosetta Encounter).

Just to report, my take & a few snippets picked up, the images from closest approach are EVEN better than anticipated. The whole of 21 Lutetia at closest approach was seen to 60 metre resolution, due to the precise tracking of Rosetta. 95 metre resolution was anticipated, but 60 being achieved, is just astonishing.

Also 21 Lutetia appears to me (I have been working on a few images, see previous posts) to be a primitive Type C body, though without compositional data, cannot say for sure.

There is a large basin, over 100 KM wide on the 130 KM wide asteroid, there are grooves, very similar to those on the Mars moon Phobos & the few seen on asteroid 951 Gaspra, as seen by the Jupiter bound Galileo Spacecraft.

There are boulders, craters of all sizes, a landslide in at least one crater & the shape of 21 Lutetia is multifaceted (that was expected). There are virtually no changes in albedo.

Later today, Sunday 11th July 2010, there will be full colour images & maybe more B & W imagery. The image from 80,000 KM looking reddish was taken through a red filter & is not actual colour, although 21 Lutetia, may turn out reddish, we'll see.

To me, the approach to 21 Lutetia suggests to me that the large 130 KM wide asteroid rotates in a prograde direction, west to east like Earth & that 21 Lutetia may have been caught near an equinox, based on how the appearance of the shape of 21 Lutetia during approach seem to suggest an equinoxial approach. 21 Lutetia is thought to rotate at a tilt of 85 degrees, on it's side basically, once every 8 hours & 10 minutes.

There appear to be no moons orbiting 21 Lutetia unlike 243 Ida.

Some craters appear to have dark floors like asteroid 243 Ida as seen by the Jupiter bound Galileo Spacecraft.

Other data, concerning potential dust, outgassings & fields & particles will be released later.

Andrew Brown.

The front end looks to be caked in ice, the big depression has snow drifts and the rims of craters are icy quite a way back. Could be a future Olympic skiing site. I would guess mostly water, but other gases could be mixed in from impacts and such. The rest looks pretty dust covered. The mass should point to the makeup. Subtract the mass of the Ice and the make-up should be clearer.

 

[orionrider]

Could be a future Olympic skiing site.

:lol:

I'm not sure about the nature of the 'soil', but these striations certainly look like a ski slope. As if something dragged or rolled on the surface... :?

http://www.traveladventures.org/contine ... iing12.jpg

Any idea of how these structures appear :?:
With the lower gravity and no air, wouldn't a boulder 'falling' from the highest 'peak' keep rolling around the world until ground friction kills its momentum, creating grooves in the 'fluffy' ground?

 

[MeteorWayne]

Despite their prevelance on small solar system objects, I have seen no consensus emerge on an explanation.

Gravity is kind of low for a boulder to create such large grooves on many of them, then there's the issue of the parallel nature, and no visible boulders...

MW

 

[kg]

Despite their prevelance on small solar system objects, I have seen no consensus emerge on an explanation....
MW

I read somewhere that similar grooves on Phobos might have been caused by vibrations from impacts propagating through the object. Any merit to this idea?

 

[orionrider]

there's the issue of the parallel nature, and no visible boulders...

It looks like scars. If the asteroid was to traverse a 'cloud' of boulder-sized objects with a low delta-v, some would impact, but others at a shallower angle and with just the right amount of velocity vs local gravity would maybe dig grooves around the sides. That could only happen to a relatively small, faceted object, like Lutetia or Phobos :?:

Phobos: http://news.nationalgeographic.com/news ... OS_461.jpg

 

[3488]

Hi orionrider,

Interesting, I see the attractiveness of Phobos & or 21 Lutetia ploughing through impact debris creating the grooves. With Phobos, it is easier to find a source, possible impact debris tossed up into near Mars space by basin forming events, namely Hellas, Argyre, Schiaparelli , etc.

With 21 Lutetia however there are no such obvious sources. There is no evidence I'm aware of that 21 Lutetia has ever been anywhere near such a source, in fact I suspect the orbit of 21 Lutetia has not changed much since the formation of the Solar System.

Closer examination of the closest approach image also show that not all grooves radiate from the basin, as might be expected if the basin was the cause, I think there are three or even four sets of grooves on 21 Lutetia. It now seems with Phobos, that Stickney Crater is not the source of the grooves on the Martian moon either & that like 21 Lutetia, Phobos too has more than one set of grooves.

Main belt asteroid 951 Gaspra has a few short stubby grooves, Mars moon Deimos & Main Belt asteroids 253 Mathilde & 2867 Šteins lack significant grooves, 253 Ida & 433 Eros have only a very few (243 Ida has only a few in one area), where as the Mars moon Phobos & Asteroid 21 Lutetia has them in abundance.

We'll see if 4 Vesta or 1 Ceres have or lack them as well as others in the future, perhaps 2 Pallas, 10 Hygiea, 29 Amphitrite (which would have been encountered had the Jupiter Galileo Spacecraft been launched in May 1986) or 66 Maja (which was a potential Cassini spacecraft encounter target on route for Saturn), etc.

Interesting stuff.

Below an enlarged, contrast enhanced, sharpened crop of a 17.5 KM wide section of the large basin on the eastern side, showing parallel grooves on 21 Lutetia & these look very much like many of those on the Mars moon Phobos.

Andrew Brown.

 

[MarkStanaway]

Could the different sets of striations seen on both Lutetia and Phobos be the result of different rotation axes in the past?
I can imagine these bodies presenting a different leading edge at various times in the past as they ploughed through diffuse debris fields.

Mark

 

[scottb50]

Could the different sets of striations seen on both Lutetia and Phobos be the result of different rotation axes in the past?
I can imagine these bodies presenting a different leading edge at various times in the past as they ploughed through diffuse debris fields.

Mark

Maybe what you see is rocks that rolled down the ski hill and up the back to roll back down and repeat the process.

To me it looked like snow drifts more then ski slopes, maybe enough atmosphere from melting ice.

 

[orionrider]

Could the different sets of striations seen on both Lutetia and Phobos be the result of different rotation axes in the past?
Mark

I think the vector of the debris field is more significant than the rotation of the asteroid. An asteroid keeping the same rotation axe could get impacted at different times by debris coming from different directions, creating several sets of parallel striations. Study of the images could reveal the sequence of striation events.

With Phobos, it is easier to find a source, possible impact debris tossed up into near Mars space by basin forming events[...] With 21 Lutetia however there are no such obvious sources.

A 'Cloud' of boulders would not survive for long. Any dV would disperse them instantly otherwise gravity would rapidly coalesce the boulders in one or more 'rubble pile' object(s). So I concur the striations have to come from an impact event in the vicinity of the asteroid.
For Lutetia there are no obvious sources, yet Lutetia has been impacted, as confirmed by the numerous craters. We assume these craters were formed in distinct random events, one at a time over billions of years. Maybe not. Maybe the asteroid was bombarded by the kind of 'shotgun effect' that could create the striations early in its history. Maybe the striations on Phobos also happened well before it became a moon of Mars :?: Again, study of the images could reveal crater groups and maybe correlate them to striation events.
This all points to a violent past, when collisions of smaller objects were very common in the solar system, maybe even before planet formation :shock:

http://solarsystem.nasa.gov/scitech/dis ... ?ST_ID=446

Fascinating stuff! :mrgreen:

 

[3488]

What will be very interesting will be when the images on closest to both sides of closest approach are released as the patterns of grooves will make more sense from varying perspectives close to closest approach. We'll have to wait for those.

Another nice mystery here, are the craters with darkened floors. Crop of an area approx 45 KM wide on 21 Lutetia, showing said craters.

Similar was also seen on type S Main Belt Asteroid 243 Ida, Galileo Spacecraft August 1993. Area approx 30 KM wide.

Any suggestions??????

Andrew Brown.

 

[scottb50]

What will be very interesting will be when the images on closest to both sides of closest approach are released as the patterns of grooves will make more sense from varying perspectives close to closest approach. We'll have to wait for those.

Another nice mystery here, are the craters with darkened floors. Crop of an area approx 45 KM wide on 21 Lutetia, showing said craters.

Similar was also seen on type S Main Belt Asteroid 243 Ida, Galileo Spacecraft August 1993. Area approx 30 KM wide.

Any suggestions??????

Andrew Brown.

It looks like most of the impacts were from an angle which means the momentum of the asteroid intercepted the object, not that it smacked into the asteroid. Those impacts, seen at different angles, show the bottom of craters being similar to other surfaces. It also looks like debris from the collisions eventually falls to the surface as fine dust especially looking at overlapping impacts and the edges of the resulting impacts, older are less defined and the relatively uniform surface of both body's, as well as others seen upclose.

 

[MeteorWayne]

If you look at it realistically scott, there's no difference between "the momentum of the asteroid intercepted the object, not that it smacked into the asteroid", they are the same, all that matters is the relative velocity, and to a lesser extant, the masses.

 

[orionrider]

Any suggestions??????

Ah, just a raw idea:

Back 4.5 billion years. :mrgreen:
On this brand-new, small, low gravity world, the ground is not really solid, it's a conglomerate of chunks and grains of all sizes ('rubble pile'). Any large impact 'shakes' it, compacting a bit more, rearranging the pieces until it gets fairly dense, with less vacuum pockets. Now the idea is that with the low gravity, the dynamics of all the parts that compose the asteroid would be more similar to a liquid than a solid. A fast forward video capturing the first millions of years of asteroid activity would show 'bubbles' of light material coming to the surface, to 'float' on the heavier stuff. Smaller asteroids impact the surface, break into pieces that slowly sink to their 'density depth'.
After a while, the asteroid grows to it's current size and is compact enough that its constituents become physically interlocked, maybe also 'fused' by internal heat (atomic decay). The asteroid is now large and compact enough to behave like a solid.
A slice of asteroid as it is today would show a metal-rich core, covered with silicates, maybe some carbon-based stuff, all blanketed by a loose mix of water and dry ice, like a fluffy snow. The final shallow coat of recent dust and debris caused by smaller impacts prevents ice sublimation. Boulders would still 'sink', to rest just under the ice.

New craters show the darker 'rock' underneath the 'snow' :idea:

Sounds credible to me. Now please someone write a computer model and let it run for a few billion years...