Starship Asterisk*

http://www.planetary.org/blog/article/00002198/ wrote:
Q: "The Mars Exploration Rover Opportunity has been studying a lot of meteorites. That made me wonder, why study meteorites on Mars when we can study them in hand on Earth? How are Mars meteorites interesting?"
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Are meteorites on Mars actually interesting?
By Emily Lakdawalla | Nov. 9, 2009

<<It's true that it's far easier to study meteorites on Earth than on Mars. Opportunity examines the meteorites it finds on Mars not to learn more about meteorites, but to learn more about Mars.

The meteorites at Meridiani planum have, in all likelihood, been sitting there for a very long time. During that time, they have interacted chemically and geologically with the surface and near-surface atmosphere, so their current composition can tell us about chemical behavior on Mars.

One of the meteorites, a metallic one named Block Island, has given us an important clue to Mars' past just by virtue of its large size. At the current thickness of Mars' atmosphere, a meteorite the size of Block Island would have disintegrated into much smaller fragments on impact with the Martian surface. So the meteorite must have fallen at a time when Mars had a significantly thicker atmosphere that would have decelerated the meteorite, slowing its crash into the ground.

Also, Opportunity's chemical analysis instruments observed varying composition on different parts of Block Island, which may indicate different states of alteration. Since meteorites are a fairly well-studied class of objects, we know a lot about what the starting composition must have been, so the current chemical composition can provide important clues to the chemistry that has operated on the Red Planet since the meteorite fell.>>

http://www.planetary.org/blog/article/00002096/ wrote:

BMAONE23 wrote:Iron will react with the oxygen in water (H-O-H) to create ferrous oxide, why not he oxygen in carbon dioxide (O-C-O)?

• <<In August, 2008, the Phoenix Lander conducted simple chemistry experiments, mixing water from Earth with Martian soil in an attempt to test its pH, and discovered traces of the salt perchlorate, while also confirming many scientists theories that the Martian surface was considerably basic, measuring at 8.3.>>

http://en.wikipedia.org/wiki/Rust wrote:
Rust is a general term for a series of iron oxides, usually red oxides, formed by the reaction of iron and oxygen in the presence of water or air moisture. Rust consists of hydrated iron(III) oxides Fe2O3·nH2O and iron(III) oxide-hydroxide (FeO(OH), Fe(OH)3). Rusting is the common term for corrosion of iron and its alloys, such as steel. Given sufficient time, oxygen, and water, any iron mass eventually converts entirely to rust and disintegrates.
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The rusting of iron is an electrochemical process that begins with the transfer of electrons from iron to oxygen. The rate of corrosion is affected by water and accelerated by electrolytes, as illustrated by the effects of road salt on the corrosion of automobiles. The key reaction is the reduction of oxygen:

O2 + 4 e- + 2 H2O → 4 OH-

Because it forms hydroxide ions, this process is strongly affected by the presence of acid. Indeed, the corrosion of most metals by oxygen is accelerated at low pH. Providing the electrons for the above reaction is the oxidation of iron that may be described as follows:

Fe → Fe2+ + 2 e−

The following redox reaction also occurs in the presence of water and is crucial to the formation of rust:

4 Fe2+ + O2 → 4 Fe3+ + 2 O2−

When in contact with water and *oxygen, or other strong oxidants and/or acids* , iron will rust. If salt is present as, for example, in salt water, it tends to rust more quickly, as a result of the electro-chemical reactions. Iron metal is relatively unaffected by pure water or by dry oxygen. As with other metals, a tightly adhering oxide coating, a passivation layer, protects the bulk iron from further oxidation. Thus, the conversion of the passivating iron oxide layer to rust results from the combined action of two agents, usually oxygen and water. Other degrading solutions are sulfur dioxide in water and *carbon dioxide in water* . Under these corrosive conditions, iron(III) species are formed. Unlike iron(II) oxides, iron(III) oxides are not passivating because these materials do not adhere to the bulk metal. As these iron(III) compounds form and flake off from the surface, fresh iron is exposed, and the corrosion process continues until all of the iron(0) is either consumed or all of the oxygen, water, carbon dioxide, or sulfur dioxide in the system are removed or consumed.

BMAONE23 wrote:Iron will react with the oxygen in water (H-O-H) to create ferris oxide, why not he oxygen in carbon dioxide (O-C-O)?

neufer wrote:

BMAONE23 wrote:Given the Iron content, I would think that the remainder would be rusty colored
if it sat in a moist environment or fell onto wet mud.

One also needs oxygen to rust.
(Rust on Earth is mostly the fault of plant life not water.)

• The atmosphere on Mars consists of
  95% carbon dioxide,
  3% nitrogen,
  1.6% argon, and
  traces of oxygen & water.

http://www.planetary.org/blog/article/00002050/ wrote:
________ Opportunity & Block Island


<<The HiRISE image of Victoria crater taken on July 19, 2009 also included the Mars Exploration Rover Opportunity (left) and the meteorite it would soon backtrack to study, Block Island (right). Credit: NASA / JPL / UA>>

bsk wrote:could somebody tell me why there is no hole/crater under the block (meteorite) shown on the picture? Surely the block when it hit Mars should have produce a hole?

thanks
BSK

Alicia wrote:Hello
If the rock found on Mars dubbed Block Island is a meteorite, Where is the crater?
Thank you.

Alicia

pacfandave wrote:A fallen meteor? And yet there is no crater and no surface material blown up around it. Perhaps it hit somewhere else and then rolled to its present location, the Martian wind having eradicated it's path.

janndave wrote:When I looked at the picture today on the site I couldn't figure out where the divot was from the meteorite landing Mars. What's the deal? Help!

nealgalt wrote:I wonder why there is no evidense of impact in the photo...crater, etc. The meteorite is on top of the soil.???????? Neal

BMAONE23 wrote:Given the Iron content, I would think that the remainder would be rusty colored
if it sat in a moist environment or fell onto wet mud.

• The atmosphere on Mars consists of
  95% carbon dioxide,
  3% nitrogen,
  1.6% argon, and
  traces of oxygen & water.

smita wrote:Could someone please tell me what are the white (lighter-shade) patches around Block Island?

Thanks.

rstevenson wrote:You folks exhibit a paucity of imagination. Think long time scale; think tens of millions of years, perhaps as much as a billion.

Imagine the rock reaching, as they said, terminal velocity and then falling into a large, thick sand dune, or maybe a deep mud puddle if Mars happened to be wetter then. Then imagine it gradually settling down as the surrounding materials erode away, first perhaps through water erosion, then later through wind erosion. Given this scenario there is little likelihood we'd see any trace of an impact crater even if one had been created originally.

As for the white rocks shown nearby, they're in evidence in many of the photos from Endeavor, and have been discussed (elsewhere if not here) at great length. You could have a look here for more info... http://marsrovers.jpl.nasa.gov/mission/ ... tyAll.html

neufer wrote:

http://en.wikipedia.org/wiki/Endeavour_(crater) wrote:<<Endeavour is an impact crater located in Meridiani Planum on Mars. Since August of 2008, Mars Exploration Rover-B Opportunity has been travelling towards it. Endeavour is 22 kilometers (13.70 miles) in diameter which compares to Victoria crater which is 750 meters (.47 miles), Endurance crater which is 130 meters (.08 miles), and Eagle crater which is 22 meters (.01 miles). Based on the amount of time it had taken to drive from Victoria it was estimated that it would take over one Martian year (23 months) for Opportunity to reach Endeavour.>>

• Crater ________ Diameter in meters
  --------------------------------------------------------------
  Chicxulub _________ 170,000
  Endeavour __________22,000
  Barringer ___________ 1,200
  Victoria ______________ 750
  Endurance ____________130
  Eagle _________________ 22

http://en.wikipedia.org/wiki/Endeavour_(crater) wrote:
<<Endeavour is an impact crater located in Meridiani Planum on Mars. Since August of 2008, Mars Exploration Rover-B Opportunity has been travelling towards it. Endeavour is 22 kilometers (13.70 miles) in diameter which compares to Victoria crater which is 750 meters (.47 miles), Endurance crater which is 130 meters (.08 miles), and Eagle crater which is 22 meters (.01 miles). Based on the amount of time it had taken to drive from Victoria it was estimated that it would take over one Martian year (23 months) for Opportunity to reach Endeavour.>>

• Crater ________ Diameter in meters
  --------------------------------------------------------------
  Aitken ___________ 2,500,000
  Turgis_____________ 580,000
  Schiaparelli________ 460,000
  Chicxulub _________ 170,000
  Endeavour __________22,000
  Barringer ___________ 1,200
  Victoria ______________ 750
  Endurance ____________130
  Eagle _________________ 22

orin stepanek wrote:Thanks Art for the color view of Block Island Meteorite! I'm amazed at the impact craters on the small meteorite.
Or are they the result of intense heat during the formation of the rock. What a story it could tell.

http://en.wikipedia.org/wiki/Willamette_Meteorite wrote:
Willamette Meteorite at the American Museum of Natural History
Iron : IIIAB : Medium Octahedrite
7.62% Ni, 18.6ppm Ga, 37.3ppm Ge, 4.7ppm Ir
Total Known Weight (TKW) 14150 kg



<<The Willamette Meteorite, officially named Willamette, is an iron-nickel meteorite discovered in the U.S. state of Oregon. It is the largest meteorite found in the United States and the sixth largest in the world. No impact crater was preserved at the discovery site; it is possible that the meteorite landed in what is now Canada and was transported to where it was found by moving ice sheets. It is currently on display at the American Museum of Natural History.

The Willamette Meteorite weighs about 32,000 pounds or 15.5 tons. It is classified as a type III iron meteorite, being composed of over 91% iron and 7.62% nickel, with traces of cobalt and phosphorus. The approximate dimensions of the meteorite are 10 feet (3.05 m) tall by 6.5 feet (1.98 m) wide by 4.25 feet (1.3 m) deep.

The distinctive pitting on the surface of the meteorite is believed to have resulted from both its high-speed atmospheric entry and subsequent weathering. In the case of weathering, rainwater interacted with the mineral troilite, resulting in a form of sulfuric acid which slowly dissolved portions of the meteorite. This resulted (over a very long period) in many of the pits that are visible today. Willamette has a recrystallized structure with only traces of a medium Widmanstätten pattern, it is the result of a significant impact-heating event on the parent body.
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http://en.wikipedia.org/wiki/Canyon_Diablo_(meteorite) wrote:
The young 50,000 year old Canyon Diablo meteorite
7.1% Ni; 1% S; 1% C; 0.46% Co; 0.26% P; 320ppm Ge; 80ppm Ga; 1.9ppm Ir

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http://en.wikipedia.org/wiki/Pyrrhotite wrote:
<<Pyrrhotite is an unusual iron sulfide mineral with a variable iron content: Fe(1-x)S (x = 0 to 0.2). The FeS endmember is known as troilite. Pyrrhotite is also called magnetic pyrite because the color is similar to pyrite and it is weakly magnetic. Pure troilite is non-magnetic. Troilite is rarely found as a native mineral on Earth, but is abundant in meteorites, in particular those originating from the Moon and Mars. Uniform presence of troilite on the Moon and possibly on Mars has been confirmed by the Apollo, Viking and Phobos space probes. The relative intensities of isotopes of sulfur are rather constant in meteorites as compared to the Earth minerals, and therefore troilite from Canyon Diablo meteorite is chosen as the international sulfur isotope ratio standard. Troilite is named after Italian abbot Domenico Troili who first noted the mineral in a meteorite that fell in 1766 at Albareto, Modena (Italy). Troili wrote the first description of the fall of a meteorite in a 43-page document published in 1766. He collected reports from many eyewitnesses, closely examined the stone and detected in it small grains of a brassy mineral he called "marchesita", which was long assumed to be pyrite, FeS2. However, in 1862, German mineralogist Gustav Rose analyzed the composition and determined it as FeS. Rose named this new mineral troilite after Troili.>>

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Modern history

The Willamette Meteorite was discovered in the Willamette Valley of Oregon near the modern city of West Linn. Although apparently known to Native Americans, its modern discovery was made by settler Ellis Hughes in 1902. At that time the land was owned by the Oregon Iron and Steel Company. Hughes recognized the meteorite's significance, and in an attempt to claim ownership, secretly moved it to his own land. This involved 90 days of hard work to cover the 3/4 mile (1200 m) distance. The move was discovered, and after a lawsuit, the Oregon Supreme Court held that Oregon Iron and Steel Company was the legal owner. Oregon Iron Co. v. Hughes, 47 Or 313, 82 P 572 (1905).



In 1905 the meteorite was purchased by Mrs. William E. Dodge for $26,000. After being displayed at the Lewis and Clark Centennial Exposition, it was donated to the American Museum of Natural History in New York City where it is now on display.

The meteorite was an object venerated by the Native American tribe inhabiting the area where it was found. The Confederated Tribes of the Grand Ronde Community of Oregon, a confederation of Native American tribes, used the meteorite, which they call Tomanowos, in an annual ceremony, and have requested that it be returned. The tribes reached an agreement with the museum in 2000. This states that tribal members may conduct a private ceremony around the meteorite once a year, and that ownership will be transferred to them should the museum stop using it for display.>>

Alicia wrote:If the rock found on Mars dubbed Block Island is a meteorite, Where is the crater?

pacfandave wrote:A fallen meteor? And yet there is no crater and no surface material blown up around it. Perhaps it hit somewhere else and then rolled to its present location, the Martian wind having eradicated it's path.

http://www.astronomynow.com/090113Marsrocksareonthemove.html wrote:
Mars rocks are on the move
BY DR EMILY BALDWIN
ASTRONOMY NOW Posted: 09 January, 2009

<<Contrary to a previous explanation that suggested high speed winds were responsible for rolling rocks around the red planet, a new model shows that a much more ordered system transports rocks upwind.

Recent images taken by the Mars Exploration Rover Spirit show small rocks regularly spaced about five to seven centimetres apart, in organised patterns, on the plains between Lahontan Crater and the Columbia Hills. One previous explanation suggested that the rocks – some of which are as large as footballs – were picked up and carried downwind by winds reaching several hundred metres per second (at a height of two metres above the ground). This is much higher than wind speeds observed on Mars today, so the authors concluded that the patterns were created in a much windier Mars of the past.


The Spirit rover took these images of evenly space rocks on Mars. Image courtesy J. Pelletier, UA.

In a new study, Jon Pelletier, associate professor of geosciences at the University of Arizona, suggests that the wind works in a different way to slowly tease the rocks from one place to another. Moreover, Pelletier’s model sees the rocks moving upwind. "My model requires only enough wind to pick up sand, about 10-20 metres per second at two metre height," he tells Astronomy Now.

In his model, the wind blows sand away from the front of a rock, creating a pit, and deposits it behind the rock, creating a hill. The rock then rolls forward into the pit, moving into the wind. As long as the wind continues to blow, the process is repeated and the rocks edge forward.

"You get this happening five, 10, 20 times then you start to really move these things around. They can move many times their diameter,” says Pelletier. "In a wind tunnel it takes about 10 minutes [to move their own diametrer]. On Mars it would take about the same time if the wind was strong enough. Winds are variable, so it's hard to say exactly, but if the winds are moderately strong and steady, it takes very little time."


A schematic to explain how the rocks move upwind, by rolling into pits carved out by winds blowing across the Martain plains. Image courtesy J. Pelletier, UA.

The process is similar for rock clusters, too. However, rocks in the front of the group shield those in the middle or on the edges from the wind. Because the middle and outer rocks are not directly hit by the wind, the wind creates pits to the sides of those rocks. Therefore, they roll to the side, not directly into the wind, and the cluster begins to spread out.

The finding supports previous work that one of Pelletier’s study team members had conducted thirty years ago. James Steidtmann of the University of Wyoming had studied upwind migration by using a wind tunnel to see how pebbles on sand moved in the wind. Steidtmann's research showed that the rocks moved upwind and that over time, a regular pattern emerged.

To investigate the regular patterns of the rocks on Mars, Pelletier combined three standard numerical computer models to take into account air flow, erosion and the deposition of sand, and the rocks' movement. He also conducted what is known as a Monte Carlo simulation, which applies his model over and over to a random pattern of rocks to see how they ultimately end up. Out of 1,000 simulations the rocks formed a regular pattern 90 percent of the time. As an independent verification, he also compared the pattern predicted by the numerical model to the distances between each rock and its nearest neighbour in the Mars images, and found that they were well matched.


Simulations also predict the movement of rocks from an initially random configuration (left) into a more ordered pattern (right). Image courtesy J. Pelletier, UA.

Upward migration of rocks also occurs on Earth, but is difficult to study due to interference from plants, wildlife and humans. Pelletier says that this migration could still be observed on Mars today. "If a current or future rover took images of the same location with a time span of a significant wind storm, it could be observed," he says. "The only caveat is that once the rocks develop a more ordered pattern (from a random initial one) they do not rearrange as often."

The work is reported in the January issue of the journal Geology>>