(meteorobs) Ablation Meteorites on The Ground!

[MEM]

Eric  don't rely on the BBC report is factually full of error.  The experimental 
design itself was poorly thought through IMO.

I googled "artificial meteorite" and the name of the experiment was  "STONE-6" 
or STONE 6 there is also a "STONE 5" referenced also an an abstract  is included 
below.

My recollection of the STONE 6 mission: The experiment was placed well outside 
the ring of direct ablation. Absolute loss of material from the sample holder 
makes the ablation portion of the experiment largely null.  The experiment was 
primarily to make an assessment of the possibility of a life-form within a 
meteoroid surviving entry.The experiment was a collection of 4 or 5 small 
samples attached to a metal fixture the size of a hat brim. Some broke, some 
fell out and some vaporized.  There is little scientifically to glean from the 
mission as the experiment largely failed team expectation but preformed as well 
as one 

should have expected.  One reference says it proved life could survive one news 
story says it proved it couldn't yada yada.  I know of no post flight photos of 
the experiment assembly.  There is perhaps one single online elsewhere.

"The exposure of a carbonaceous siltstone sample to atmospheric entry, as part 
of the STONE 6 artificial meteorite experiment, has allowed a controlled 
investigation of the effect of heat shock during atmospheric entry on organic 
matter in carbonaceous meteorites and, potentially, sedimentary martian 
meteorites containing carbonaceous biomolecules. Thermal alteration is evident 
in an increase in structural order of the carbon (i.e. degree of 
graphitisation), preferential loss of thermally unstable compounds and 
substantial loss of extractable organic matter. There is a gradient of 
increasing alteration towards the outer, exposed margin of the rock, and also an 
increase in hydrocarbons that suggests outward migration following 
thermally-induced generation. The carbon has not been completely graphitised, 
and sufficient biomarker compounds survive to prove the biological origin of the 
organic matter. The experiment implies that meteorites of appropriate size could 
preserve evidence of biological activity on their parent body". 


also

"The generic concept of the artificial meteorite experiment STONE is to fix rock 
samples bearing microorganisms on the heat shield of a recoverable space capsule 
and to study their modifications during atmospheric re-entry. The STONE-5 
experiment was performed mainly to answer astrobiological questions. The rock 
samples mounted on the heat shield were used (i) as a carrier for microorganisms 
and (ii) as internal control to verify whether physical conditions during 
atmospheric re-entry were comparable to those experienced by “real” meteorites. 
Samples of dolerite (an igneous rock), sandstone (a sedimentary rock), and 
gneiss impactite from Haughton Crater carrying endolithiccyanobacteria were 
fixed to the heat shield of the unmanned recoverable capsule FOTON-M2. Holes 
drilled on the back side of each rock sample were loaded with bacterial and 
fungal spores and with dried vegetative cryptoendoliths. The front of the 
gneissic sample was also soaked with cryptoendoliths. The mineralogical 
differences between pre- and post-flight samples are detailed. Despite intense 
ablation resulting in deeply eroded samples, all rocks in part survived 
atmospheric re-entry. Temperatures attained during re-entry were high enough to 
melt dolerite, silica, and the gneiss impactite sample. The formation of fusion 
crusts in STONE-5 was a real novelty and strengthens the link with real 
meteorites. The exposed part of the dolerite is covered by a fusion crust 
consisting of silicate glass formed from the rock sample with an admixture of 
holder material (silica). Compositionally, the fusion crust varies from 
silica-rich areas (undissolved silica fibres of the holder material) to areas 
whose composition is “basaltic”. Likewise, the fusion crust on the exposed 
gneiss surface was formed from gneiss with an admixture of holder material. The 
corresponding composition of the fusion crust varies from silica-rich areas to 
areas with “gneiss” composition (main component potassium-rich feldspar). The 
sandstone sample was retrieved intact and did not develop a fusion crust. 
Thermal decomposition of the calcite matrix followed by disintegration and 
liberation of the silicate grains prevented the formation of a melt. 
Furthermore, the non-exposed surface of all samples experienced strong thermal 
alterations. Hot gases released during ablation pervaded the empty space between 
sample and sample holder leading to intense local heating. The intense heating 
below the protective sample holder led to surface melting of the dolerite rock 
and to the formation of calcium-silicate rims on quartz grains in the sandstone 
sample". 


STONE 5

Response of sandstone to atmospheric heating during the STONE 5  experiment: 
Implications for the palaeofluid record in meteorites 




References and further reading may be available for this article. To view 
references and further reading you must purchase this article.


John Parnell, Darren Mark and Franz Brandstätter

Abstract
A 1 cm thick sandstone disk exposed to  atmospheric re-entry on the heat shield 
of a spacecraft (the STONE 5  experiment) shows alteration of fluid inclusions 
compared to a control  sample. The sandstone contained inclusions in quartz 
grains, feldspar  grains and calcite cement before flight. After flight, 
inclusions in the  feldspar were all decrepitated, few inclusions in calcite 
survived  intact and they yielded widely varying microthermometric data, and the  
quartz inclusions also yielded disturbed microthermometric data. The  quartz 
becomes less affected with depth below the surface, and  extrapolation suggests 
would be unaffected at a depth of about 2 cm.  These data show that fluid 
inclusion data from meteorites must be  treated with caution, but that a genuine 
fluid record may survive in the  interior portions. The possibility of thermal 
sterilization to 2 cm  depth also implies that small meteorites may be 
unsuitable vehicles for  the transfer of microbial life from one planetary body 
to another. As  the interiors of larger meteorites tend to have very low 
porosity and  permeability, microbial colonization would be difficult, and the  
potential for panspermia is accordingly low.

Elton




----- Original Message ----
> From: Meteorites USA <eric at meteoritesusa.com>
> To: meteorobs at meteorobs.org
> Sent: Sat, March 26, 2011 4:33:32 PM
> Subject: Re: (meteorobs) Meteorites on The Ground! (Was: To Dirk)
> 
> Hi Marco, List,
> 
> Your point seems logical, but I have a few questions.  Basically the 
> ablation rates of the artificial meteorite was determined with  an object 
> that fell at 35% of the speed of a natural meteoroid. Slower  right? So 
> given that it was falling slower, and was incandescent for a  longer 
> period, wouldn't that mean that it would have more time to ablate? 
> Perhaps a lower temperature for a longer duration, would be comparable 
> to a higher temperature for a shorter duration. Would it not ablate 
> comparatively to a larger faster  body?
> 
> Regards,
> Eric
> 
> 
> 
> 
> On 3/26/2011 5:26 AM, Marco Langbroek wrote:
> > Op 26-3-2011 00:45, Meteorites USA schreef:
> >    
> >> Quote: ""Three quarters of the rock,  which was about the size of a small
> >> pork pie, was burnt off in the  experiment."
> >>
> >> So only 75% of a body is ablated during  atmospheric entry? This
> >> disproves the 90% ablation rate hypothesis  and actually proves my point.
> >>      
> >
> >  It disproves nothing. Apples and oranges.
> >
> > Somebody here on meteorobs already remarked this earlier: but the entry 
>velocity
> > of an  earth orbiting vehicle (i.e. satellite) such as the one on which the
> >  samples were mounted, is clearly lower than that of meteorite dropping
> >  meteoroids. As a result, ablation rates will be markedly  different.
> >
> > Re-entry from Earth orbit is with maximum speeds of  7.5 - 8 km/s. This is a 
>mere
> > 35% to at best 50% of the speed of a  meteoroid (minimal 11.8 km/s, often 
>much
> > more, up to 25  km/s).
> >
> > In a way, this is somewhat similar to having a bicyclist  at ~30 km/h run 
>into a
> > wall, and then trying to asses from that what  damage will result from a car
> > doing the same at 100  km/h.
> >
> > The two are just not comparable.
> >
> > -  Marco
> >
> >
> > -----
> > Dr Marco (asteroid 183294) Langbroek
> > Dutch Meteor Society (DMS)
> >
> > e-mail: dms at marcolangbroek.nl
> >  http://www.dmsweb.org
> > http://www.marcolangbroek.nl