MSL - Stopover on the Road to Glenelg - Arm Commissioning, Commissioning Activity Period 2 - Sols 30 through 37 Options

[Deimos]

... I haven't noticed any solar filter images from MSL yet.

Neither have I. Ah well, good things come to those who wait. (And maybe even to those who pester people until they get good things ...)

[Doc]

Speaking of dented wheels, what exactly is the material used for Curiosity's wheels (heavy duty plastic or fiberglass)?

[nilstycho]

Speaking of dented wheels, what exactly is the material used for Curiosity's wheels (heavy duty plastic or fiberglass)?

Curiosity’s wheels are aluminum, 20 inches (0.5 meter) in diameter, which is twice the size of the wheels on Spirit and Opportunity. They have cleats for traction and for structural support. Curving titanium spokes give springy support. The wheels were machined by Tapemation, Scotts Valley, Calif. Titanium tubing for the suspension system came from Litespeed Titanium, Chattanooga, Tenn.

Mars Science Laboratory Landing Press Kit

[jmknapp]

An anaglyph of the interesting rock:



The piece in the background seems to be the same stuff--maybe it broke off the base piece leaving the relatively fresh surface?

[Doc]

Mars Science Laboratory Landing Press Kit

Thanks nilstycho. Aluminium it is.

[Pando]

Contrast and color enhanced to bring out some interesting features. There is definitely some slight greenish tinge present in that rock.

Attached thumbnail(s)

 

[Reckless]

From sadly not a geologist, this looks a bit like andesite which on earth is often associated with tectonics but I noticed on Wikipedia that two meteorites were found with andesite in suggesting another method of producing it, maybe Curiosity has found another example.
I hope we get more information on this rock.
The meteorites in question are numbered GRA 06128 and GRA 06129 found in Alaska.

Roy

[elakdawalla]

You have to be careful with casual rock identifications. There are two major things that affect an igneous rock's appearance: composition, and the rate at which it cooled. The terminology can be confusing. Basalt, andesite, and rhyolite have very different compositions but can have very similar looking textures because the texture is controlled more by the cooling rate than by composition; those three are the names for the rocks with fine-grained textures. The same magmas would produce gabbro, diorite, or granite (respectively) if allowed to cool more slowly. You can't tell just by looking at a rock from a distance whether it's basalt or andesite. On Earth, most of our oceanic crust is basalt, while most continental crustal rocks have bulk compositions closer to the rhyolite end (very little Mg, Fe, but lots of Al and Si and lighter metals like K and Na), so when you come across a new rock you have to entertain the entire possible range of compositions as possibilities. On Mars, basically everything has a basaltic bulk composition; the safe assumption is that it's basaltic until your chemical analysis instruments (either remote sensing or in situ) tell you otherwise.

To understand how you can make andesitic magmas from basaltic parent rocks, look up "partial melting" and "fractional crystallization." Nobody should make statements about igneous rock composition until you understand what those two terms mean!

[Zeke4ther]

Thanks for that, Emily. I did a search and it was very enlightening.

Though the processes would be similar, it made me think just how alien the Martian environment is and how it would effect what we see.

[Doc]

Judging from the size of the crystals, we can safely say that it is intrusive type of igneous. That at least should help identifying (or am I just kidding myself?)

We ought to keep a 'rock photojournal' for this voyage. I used to collect many rocks and id them when still a wee lad. Now its just MD for me

[Don1]

Olivine is a green mineral.

[Pando]

I am curious - would a smaller gravity on Mars have an effect on how the rocks are formed? Most of the assumptions about rock compositions are made based on Earth-based geology, but how closely does it translate to the environment on Mars?

[elakdawalla]

Big crystals do have to form at depth, but you can have rocks with crystals that formed at depth but then the crystals were entrained in a liquid magma that reached the surface & cooled rapidly. (Look up "porphyritic")

The lower gravity doesn't change much, because most rocks form at depth under pressure. What does change is the depths at which certain kinds of rocks form. I was talking with some people who run a rock-squishing lab at APL and they told me their apparatus could crush rocks to the pressures encountered near the core of the Moon, at the base of the mantle of Mercury, but only in the upper mantle of Earth.

The lower air pressure does change the behavior of eruptions. On one end you get Venus where every kind of lava extrudes & doesn't explode; on the other end you get Io, where any trace of gas in a magma violently exsolves upon eruption, causing tall ash plumes. You'd expect volcanism on Mars to be more explosive than volcanism on Earth for that reason.

[ngunn]

The lower air pressure does change the behavior of eruptions. On one end you get Venus where every kind of lava extrudes & doesn't explode; on the other end you get Io, where any trace of gas in a magma violently exsolves upon eruption, causing tall ash plumes. You'd expect volcanism on Mars to be more explosive than volcanism on Earth for that reason.

A brilliant and succinct explanation! I love the idea of a spectrum ranging from Venus to Io with all the other worlds in between.
Just one thing to add: liquids. Submarine eruptions here can find themselves in a Venus-like pressure regime. The same may once have been true on Mars.

EDIT: Maybe we should add Europa. What are eruptions like at the bottom of that ocean?

[dvandorn]

Considering that Sojourner's APXS identified some of the rocks it examined in Ares Vallis as andesitic, I can understand how someone might look at a basaltic rock on Mars like the one we've been discussing, with such large crystals, and make a preliminary identification of andesite.

-the other Doug