ESA Rosetta to 67P/Churyumov-Gerasimenko.

[3488]

I will be posting properly later. My mental health has taken a very serious dip, attempted suicide yesterday & had to spend quite a few hours last night in hospital.

After a mega dose of medication given to me by the doctor in hospital, I was allowed home, slept all morning & now just trying to drum up enthusiasm.

Thought I would try with this.

Below, Emily Lakdawalla has created a new montage of asteroids & comets to scale, with 21 Lutetia included. Shows how large she really is.

Below is all credit to Emily Lakdawalla.


I will be back later, have an emergency doctor's appointment later.

Andrew Brown.

 

[EarthlingX]

It is a nice image to help enthusiasm

I will just drop in link to the Emily Lakdawalla's article :

http://www.planetary.org : How does Lutetia compare to the other asteroids and comets visited by spacecraft?

and i know you will get well soon.

 

[3488]

I am really struggling & not sure how long I can continue for a while, but hopefully will be better before too much longer.

Below I have attempted three enlarged sharpened contrast enhanced crops of 21 Lutetia.

30 KM wide area on the second to last one during approach of 21 Lutetia (2 minutes prior to closest approach). Both dark floored craters & grooves are visible. At closest approach this area was visible but was very highly foreshortened. Resolution was still an excellent 70 metres (still far superior to what was anticipated for closest approach)

A section of 35 KM wide section of limb rotated 90 degrees, a 5,000 metre tall mountain (was bottom left).

Same area as above but from a slightly different angle.

A 20 KM section of limb rotated 90 degrees. A few narrow grooves are visible, small dark floored craters & what looks like a valley on 21 Lutetia.

Andrew Brown.

 

[orionrider]

Brilliant, Andrew, as always
I'm sure the eclipse will not last. You'll be back in full light in no time, and I look forward to reading your excellent posts

 

[MarkStanaway]

Hang in there Andrew, they say that the night is always darkest just before dawn, but dawn will surely follow.
We need people like you with your undoubted talent to interpret features from imagery returned by various probes to the solar system. Your contributioins to these forums is invaluable and I look forward to your future analysis of data.
All the best for a speedy recovery.
Regards
Mark

 

[EarthlingX]

http://www.astronomynow.com : Rosetta looks south for landing site

DR EMILY BALDWIN

Posted: 23 September 2010

A new study of comet 67P/Churyumov-Gerasimenko reveals that the southern hemisphere of the comet will present the safest landing site for ESA's Rosetta mission to deliver its lander, Philae.

Artist's concept of Rosetta approaching Churyuomov-Gerasimenko in 2014. Image: ESA

The finding is based on three-dimensional computer models created by Jeremie Lasue and colleagues from the INAF-IASF and IFSI institutes in Rome, that predict the comet's activity during the first few months of Rosetta's encounter.

“When Philae lands, temperatures at the equator may rise above freezing and could fluctuate by around 150 degrees Celsius,” says Maria Cristina De Sanctis, co-author of the study. “However, the regions close to the south pole will keep more stable temperatures. From our present results, we’ve concluded that the southern hemisphere promises the best landing sites.”

...

Click here for animation. The author's surface illumination model of the nucleus of comet Churyumov-Gerasimenko at the time of Philae’s landing on the comet nucleus (approximately 3 AU from the Sun).

...

“Churyumov-Gerasimenko is a time capsule holding material from the birth of the Solar System,” says Lasue. “The nucleus’ southern hemisphere has been heavily eroded, so Philae will not have to drill down far to find those pristine samples. At the time of Rosetta’s rendezvous, gas will be escaping mainly from the northern hemisphere, so it will be safer for Philae to touch down in the south. In addition due to the orientation of the comet, the southern hemisphere will be protected from extreme temperature variations at the time of delivery.”

Rosetta will rendezvous with the comet in May 2014, with the lander dropping down to the surface six months later, where it will study the surface and sub-surface to determine the comet's evolution. As Rosetta approaches the comet more data will be available to hone in on the safest landing sites for Philae.

 

[orionrider]

Excellent, EarthlingX!
As always

 

[alpha_centauri]

And yet still no word from the European Planetary Science Congress on the actual preliminary results from Rosetta's Lutetia flyby despite them supposedly being presented a few days ago...

There's been plenty of news reports of other findings presented at the conference.

 

[EarthlingX]

Thanks orionrider I've seen some of your nice things, have them on the disk too

alpha_centauri : Did you check for a schedule ? I haven't seen any, so i guess it might take them some time to digest everything from that fly-by. Phobos fly-by results were just published, if that is any kind of orientation.

 

[alpha_centauri]

alpha_centauri : Did you check for a schedule ? I haven't seen any, so i guess it might take them some time to digest everything from that fly-by. Phobos fly-by results were just published, if that is any kind of orientation.

Yeah it is linked from the Europlanet website http://www.europlanet-ri.eu/epsc, organised through some website called Copernicus (the whole EPSC schedule is on it btw),

European Planetary Science Congress 2010- Rosetta flybys of 2867 Steins and 21 Lutetia

As far as I can tell from the abstracts, the oral program is where the results were presented...on tuesday! All the news stories released so far as far as I can see were embargoed until the day of their presentation. For example the presentation on Phobos was on monday according to the schedule and that article was released onto the Europlanet website on monday. The article above about the comet C-G was released today, presentation was today etc etc.

 

[EarthlingX]

Well, there are reports about making Rosetta LEGO models, cute, but don't think that answers your question ..

I checked their home page, nada. Nothing of the sort on the DLR Rosetta site, press releases or news.

If i see it, i'll drop it here.

 

[3488]

WOW already decided where they are going to land Philae :!: :!: :!: :!: :!: Near the south pole of the comet.

The percieved shape of the nucleus is interesting, quad lobed!!!!!!! Will be interesting to see the reality when Rosetta arrives.

I too have looked for 21 Lutetia updates, there are none as yet!!!!!!!

Would like to see some colour images, flyby animation, magnetometer, spectrometer & density data too. Hope that we do not have to wait long for it now.

Andrew Brown.

 

[alpha_centauri]

Perhaps the complaints paid off?

Anyway, a portent of what's to come with larger objects like Vesta?

http://www.bbc.co.uk/news/ : Asteroid Lutetia has thick blanket of debris

By Jonathan Amos
Science correspondent, BBC News

Lutetia, the giant asteroid visited by Europe's Rosetta probe in July, is covered in a thick blanket of dusty debris at least 600m (2,000ft) deep.

Aeons of impacts have pulverised the space rock to produce a shattered surface that in terms of texture is much like Earth's Moon, scientists say.

The finding is one of the first to emerge from the wealth of data gathered by Rosetta during its close flyby.

The details are being discussed this week at a conference in Pasadena, US.

Rosetta science team-members will tell the Division for Planetary Sciences (DPS) of the American Astronomical Society (AAS) that many of their discoveries will need further investigation and discussion before firm conclusions can be drawn.

Rosetta's encounter with the asteroid occurred some 454 million km (282 million miles) from Earth, beyond the orbit of Mars.

Multi-wavelength cameras and spectrometers, magnetic field and plasma experiments, dust instruments, a radio science experiment - all were tasked with gathering as much information as possible as the spacecraft whizzed by at the relative speed of 15km/s (9 miles/s) and a minimum distance of 3,162km (1,964 miles).

The data indicates Lutetia has a mass of about 1,700 trillion tonnes.

One calculation for the volume is 650 trillion cubic metres, giving a density of some 3.4 grams per cubic centimetre - not dissimilar to that of Earth (3.34g per cu cm).

 

[3488]

Thank you very much alpha_centuari. :mrgreen:

3.4 G CM[super]3[/super]. Quite a bit higher than I had expected, assuming a type C.

To me that is remarkarbly similar to a coherent solid tpye S asteroid, with perhaps some metallic enrichment. To me that seems too high for a type C, but too low for a coherent type M, though of course a rubble pile metallic asteroid my have that sort of density.

Certainly the deep regolith is not uniform. Where the striation are is certainly only thinly covered, but where the smoother profiles are, yes it's deep & thick.

I think what Aunty Beeb were trying to say was that the SILICATE (upper mantle & crust) part of the Earth has a density of approx 3.34 G CM[super]3[/super]. The Earth has an overall density is 5.517 G CM[super]3[/super], more akin to to Venus & Mercury. 3.4 G CM[super]3[/super] is more like the Moon, Mars, Europa & Io.

They kept the error that COMET 67P/Churyumov-Gerasimenko, is an asteroid!!! :shock: Us British License payers deserve the scientific accuracy of reporting by Aunty Beeb!!! :shock: :shock: :shock: :? :!: :!: :!: :!: :roll:

Andrew Brown.

 

[alpha_centauri]

Yeah I thought that too. While the density has been revised downwards due to a lower mass it is still too high for a purely carbonaceous C-type. As you say this is the sort of value for a totally solid stony asteroid even, but the low density chondrite regolith says otherwise and a solid structure is probably unlikely anyway. I think the story of this asteroid's structure and history may not be as clear as it first appeared from the pictures.

The Beeb is never wrong...Arf! To be fair though in the case of the image it's from ESA and they probably didn't look for a mistake.

EDIT: I see the density comment has been changed now to "not dissimilar to that of Earth's Moon (3.34g per cu cm)."

 

[MeteorWayne]

SDC article

"Dusty debris shrouds the huge asteroid to a depth of at least 2,000 feet (600 meters), scientists have calculated. The dust probably resembles the regolith found on the moon, and it's a result of the intense cosmic pummeling Lutetia has endured from other space rocks since the birth of the solar system. [Photo of Lutetia craters.]

"It must have been produced by impacts," said Rita Schulz of the European Space Agency in a media briefing yesterday (Oct. 4) in Pasadena, Calif. The announcement came at a conference organized by the American Astronomical Society's Division of Planetary Sciences.

A visit to Lutetia

The new look at Lutetia, which is located in the asteroid belt between Mars and Jupiter, is the result of a close fly-by made by ESA's Rosetta spacecraft in July. Rosetta, whose chief task is chasing down and studying a comet, zoomed to within 1,900 miles (3,162 km) of Lutetia, making it the largest asteroid ever to be visited by a space probe.

Rosetta snapped some detailed photos and probed the space rock from afar with a suite of instruments. The data confirmed that Lutetia is an elongated body with its longest side spanning approximately 81 miles (130 km), ESA officials have said.

But it took some time for scientists to process and analyze much of Rosetta's data. Over the last few months, they scrutinized some of Lutetia's many craters, measuring how deep they are. Researchers then compared that information with predictions of how deep such craters are expected to be based on theoretical models. "

 

[EarthlingX]

http://www.eso.org : Predicting the Size and Shape of an Asteroid at a Distance

7 October 2010



Astronomers have used the ESO Very Large Telescope (VLT), in conjunction with other telescopes, adaptive optics technology and an advanced computer program, to accurately predict the size and shape of an asteroid 200 million km from Earth. As the asteroid, (21) Lutetia, is only 100 km across, the challenging Earth-based observations were equivalent to trying to measure the size and shape of a large baked potato at a distance of about 200 km. Each of the approximately 300 snapshots shows the asteroid as little more than a small blob, but by combining all of them, together with further measurements of the brightness of the asteroid over time, the team were able to reconstruct a three-dimensional model of Lutetia.

Following this, ESA’s Rosetta spacecraft took high-resolution photographs of Lutetia during a fly-by in July 2010. The images show convincingly that the ground-based observations correctly predicted both the size and shape of the asteroid to within a few percent! Having a correct three-dimensional model of Lutetia will be invaluable for the scientists who are interpreting the data from Rosetta. This demonstrates that the combination of large Earth-based telescopes, adaptive optics technology and advanced computer code is an extremely powerful way to study asteroids.

The results, from a team led by Benoit Carry from the Observatoire de Paris, are presented at the annual meeting of the American Astronomical Society’s Division for Planetary Sciences, taking place from 3–8 October 2010 in Pasadena, California, USA.

Links
* Related press release from Southwest Research Institute (SwRI) in Boulder, Colorado, USA

 

[3488]

WOW thanks EarthlingX,

Have not seen that final image before, just after CA. Also the predicted shape from Earthbased obs were fairly accurate & even detected the giant basin on 21 Lutetia.

There is still no substitue for getting up close like Rosetta did.

Newly seen image. 21 Lutetia. 3 minutes after CA. Approx 'Last Quarter' phase.

ESA / DLR.

Andrew Brown.

 

[MeteorWayne]

Just a side note. 21 Lutetia is the largest of the 10 asteroids that have been imaged by visiting craft.

In decreasing size, they are:

21 Lutetia 132x101x76 km [Rosetta 2010]
253 Mathilde 66x48x44 km [NEAR 1997]
243 Ida 59x25x19 km [Galileo 1993]
433 Eros 33x13 km (NEAR landed on it) [NEAR 2000]
951 Gaspra 18x10x9 km [Galileo 1991]
5535 Annefrank 6.6x5.0x3.4 km [Stardust 2002]
2867 Steins 5.9x4.0 km [Rosetta 2008]
9969 Braille 2.1x1x1 km [Deep Space 1 1999]
(243 Ida 1) Dactyl 1.6x1.2 km [Galileo 1993] {Satellite of Ida}
25143 Itokawa 0.5x0.3x0.2 km [Hayabusa 2005; it probably landed and may have returned some material to Earth]

Comet Nuclei Imaged:

1P/Halley 16x8x8 km [Vega 2, Giotto, 1986]
19P/Borelly 8x4 km [Deep Space 1, 2001]
9P/Tempel 1 7.6x4.9 km [Deep Impact 2005, probe impacted surface, Now EPOXI mission rendevous with 103P/Hartley coming up this month]
81P/Wild 2 5.5x4.0x3.3 km [Stardust 2004, returned particles from Coma to Earth]

Info from News Notes, Sky and Telescope Oct 2010

MW

 

[3488]

Thanks Wayne,

It is good to see a list like that. I knew about the sizes, but seeing them listed like that is very informative.

Quite a motely crew too.

I will reciprocate, copied your list & put types & miscellaneous other notes.

21 Lutetia 132x101x76 km [Rosetta 2010] Still not clear, density type S, surface texture suggests type C or D. Rotates on its side like planet Uranus & asteroid 433 Eros. As Wayne pointed out 21 Lutetia by far is the largest asteroid seen up close to date.

253 Mathilde 66x48x44 km [NEAR 1997] Type C, Carbonaceous. Extremely slow rotator, one rotation taking just over 17 days (only asteroids 288 Glauke & 1220 Crocus take longer to rotate on their axis). Very low density with gigantic deep craters, suggesting rubble pile construction, however NEAR did measure a Mass Concentration, later identified to be located in a 'ridge' on the asteroid, so there is some solid material there.

243 Ida 59x25x19 km [Galileo 1993] Type S, Silicate Rich. Strange shape, remote possibilty of being a contact binary with rubble infill (I am doubtful). Gravity data suggests a solid coherent object.

433 Eros 33x13 km (NEAR landed on it) [NEAR 2000] Type S, Silicate Rich. Rotates on it's side like planet Uranus & asteroid 21 Lutetia. First non main belt asteroid seen up close. NEAR actually landed at the end of the mission & did return data for a while post landing. Gravity data suggests a solid coherent object.

951 Gaspra 18x10x9 km [Galileo 1991] Type S, Silicate Rich. Has some Olivine enrichment in places & has a fossil magnetosphere. Gravity data suggests a solid coherent object.

5535 Annefrank 6.6x5.0x3.4 km [Stardust 2002] Type S, Silicate rich.

2867 Steins 5.9x4.0 km [Rosetta 2008] Type E, Enstantite Achondrite type, extremely rare, one of only 27 known. Most certainly originated in the mantle of a much larger body.

9969 Braille 2.1x1x1 km [Deep Space 1 1999]. Type V, Vestarian type. Possibly a chunk knocked of giant main belt asteroid 4 Vesta. Deep Space 1 unfortunately was facing the WRONG WAY at closest approach due to a software error & took readings & images of deep space instead. What a shame.

(243 Ida 1) Dactyl 1.6x1.2 km [Galileo 1993] {Satellite of Ida} As mentioned, moon of 243 Ida, type S Silicate rich, but appears greyer & less 'red' than the parent asteroid.

25143 Itokawa 0.5x0.3x0.2 km [Hayabusa 2005; it probably landed and may have returned some material to Earth] Type S, silicate rich, rubble pile, very low density.

Fascinating topic. Looking forward to the Deep Impact Comet 103P/Hartley 2 pass in less than a month now. Next August DAWN will hopefully show us what a giant asteroid really looks like when 4 Vesta is reached. Mean diameter 468 KM!!!!!! :shock:

Andrew Brown.

 

[MeteorWayne]

Nice followup Andrew, Thanx!

 

[EarthlingX]

Thanx to both of you for putting some meat on the bones

 

[3488]

Thank You EarthlingX for providing such an excellent link & graphic.

The image I posted is a crop from the full sized image provided by your link. I was eager to see a view of 21 Lutetia from just that very angle, due to the orientation of the basin & a more full on view of the basin wall opposite to the one seen well during the approach.

Also seeing the grooves on the outcrop that were well seen during approach are now well seen from the other direction, not to mention seeing the terminator from another angle & the multifaceted shape of the huge asteroid from a different viewpoint. The high phase angle already provided by ESA was fascinating for seeing the shape of the asteroid in such a slim 'crescent' phase.

I wanted one that was in between the once from close to closest approach & that one & you by the back door provided just that.

Please if you see anything else, more about 21 Lutetia, either images or info or both, please bring it here!!!!!

You are very welcome Wayne,

I absolutely love this subject with a passion. I would love to see a dedicated or perhaps a pair of dedicated probes to take up heliocentric orbit within the Asteroid Belt & encounter one after the other, after the other over many years, perhaps like a Voyager or New Horizons clone, we know both designs work extremely well. I probably would not bother revisiting any main belt asteroid in your list with the exception of 5535 Annefrank (I felt we were a bit cheated by mission planners for not reducing the flyby distance), & 253 Mathilde, to time it so that the other side of the asteroid is in sunlight opposite to that well seen by NEAR, but that is the only reason, but the others were very well seen generally.

Andrew Brown.

 

[3488]

Fascinating update.

When is a comet not a comet? Rosetta finds out

13 October 2010
It was a case of celestial hit and run. Two asteroids, both in the wrong place at the wrong time. The result: one big trail of debris and a case of mistaken identity. Now, however, ESA’s comet-chaser Rosetta has unravelled the truth.

Using its OSIRIS camera, Rosetta made the breakthrough because it is far from Earth and so it could look at mystery object ‘P/2010 A2’ from a u..........

ESA Rosetta Spacecraft images aftermath of Asteroid P/2010 A2 collision. March 2010.

Clickable thumbnail.


ESA / DLR.

Andrew Brown.

 

[MeteorWayne]

As I said in the other thread, technically, the designation P/2010 2A means the object is being classified a comet, not an asteroid. If I have my nomenclature correct, the 26th of the year.
MW