I won't throw in any gratuitous insults other than that, though they are richly deserved.

> "Mars lacks the volcanism for round gas pockets to form, and there is no other spherical mechanism except for impact condensate."

"Well, excuse me, EP, but AT THE TIME that the meridiani deposit formed,"

Oh really. You've done the Mars surface meteorite accumulation counts to tell me when Meridiani formed, or are you deriving that date from your "blueberries"?

I point out that these "blueberries" (arghh, eat a bowlful of them) or "spherules" are found elsewhere.

" Mars had ample volcanism."

Given the current observed molten core, not at any reasonable rate of core cooling, it did not.

"Even if that were not the case,"

a note of doubt, good Doctor?

"there are other ways to make round objects - concretions for one,"

I remind you that these are not just round objects, but perfectly round objects. As for concretions, yes, but in what fluid or suspension? Perfectly round ones, lacking deep and stable fluid water?

> The size distribution is so limited "Because Mars' atmosphere and gravity are constant"

"Well so is the Eath's, but terrestrial tektites are widely variable in shape, & size, even for a single impact."

Mars atmosphere and gravity differ significantly from those found on Earth. These "spherules" are not glassy, as are Earth tectites.

> what is the source of the haematite? "Any iron impactor"

"If you knew anything about impactors and impact condensate you might be aware that:
Haematite is an iron oxide. To make it from iron, you must add oxygen.
On Mars, the only source of that is the CO2 in the atmosphere. Where is the associated reduced carbon?"

Subsumed, along with the water and CO2. It is sometimes seen on the surface at the bottom of craters, as in the images Dan Spires called to our attention several years ago, but usually it is covered with dust.

But all of this ignores other sources of oxygen. H2O would work as well, with the hydrogen lost to space by planetary outgassing.

"Anyway, on Earth, volatalised iron does not oxidise in the much higher oxygen fugacity (partial pressure) of our atmosphere. - For instance, the Canyon Diablo Iron meteorite produced a shower of mm-sized particles from its ablated surface. These are nickel-iron in composition, unoxidised. You can trawl around meteor crater Az or the eponymous Canyon with a magnet and find a whole bunch of these in the gritty soil."

Uhhh, Dr. Hotshot, it was not the "ablated surface" of the Canyon Diablo impactor which produced the spherules seen at Canyon Diablo - look it up in the meteorite list archives, along with the basic intro to hyper-velocity impacts.

After you have done that, please do not put words into my mouth.

Remember also that the Canyon Diablo area was fairly dry at the time of impact. Look to the south of the Opportunity landing site, and you cam see mud sheets surrounding the crater there

"And before you finish, can you cogently differentiate between an impact condensate formed from "hot impact dust", one formed from molten material, and one formed from vapour."

Pop quiz, eh? Okay, let's see.

"hot impact dust" will have other "dust" inclusions, and very low shatter strength, compared with glasses or "vapour" condensates.

"molten material" - glassy, long structures - low shatter strength, high shear strength. typical of Earth tektites; non molten inclusions sometimes seen

"vapour" (or vapor) - spherules form first, of different compositions; these then accrete into larger masses. individual spherules clearly seen in final accretion

"Plus, you might care to address the lack of blueberry-rich layers."

try an immediate nearby impact, more wind erosion at Meridiani, and a less dense surface rock - otherwise similar concentrations would be seen elsewhere, instead of the less dense spherule concentrations actually observed.

"It's kind of fundamental..."

yes indeed it is...

ep