Mrs. Christinao's Talented & Gifted Class
Manassas, Virginia

"What is the most common rock found on the surface of Mars?"

Evidence from the Thermal Emission Spectrometer (TES) on Mars Global Surveyor, a satellite currently orbiting Mars, indicates that Basalt or rocks of basaltic composition are the most common on the surface of Mars. TES essentially measures the amount of heat that a rock gives off after absorbing sunlight all day, and different rocks made up of different minerals will give off different amounts of heat. So far, the data received is very similar to that of basalt. Basalt is a volcanic-igneous rock and is very common on Earth, the Moon, and Mars. Common places to find basalt on Earth are Hawaii, where you can see basaltic lava erupting from Kilauea volcano. Basalt also comprises the oceanic crust, erupting at Mid-ocean Ridges. On Mars, there are shield volcanoes, similar to Hawaii, only many times larger than volcanoes on Earth. This shield morphology is very common for volcanoes comprised of basalt flows.

There is evidence for Andesite, another type of volcanic-igneous rock, but scientists think it could also be weathered basalt. Most of the suface is covered by dust, so who knows what could be lying underneath.

"How many different kinds of rocks would be found on Mars and what are the made of?"

By my count, we have evidence for 1 (basalt), possibly 2 types of ignous rocks (basalt and andesite). Andesite is a rock type found on volcanoes in the Cascade Mt. Range in the northwest United States (e.g. Mt. St. Helens) and in the Andes Moutains in South America.

There is strong evidence for sedimentary rocks in some of the images from the Mars Orbiter Camera, as well as from general interpretation of the formations on the Martian landscape that resemble river channels and lake beds. Check out This Link for some stories and photos.

But exactly what kinds of sedimentary rocks there might be on Mars (sandstones, breccias, conglomerates, mudstones, just to name a few), is still up in the air until we either have a sample return mission or send humans there to explore. Breccias, a rock with angular rock fragments/pieces held together by finer-grained material (picture large chunks of chocolate bar in a brownie, to get a visual image) can be formed from debris from impact cratering, so this is could be a possibility of a rock type to find on the surface. There is no conclusive evidence for any types of metamorphic rocks on Mars, yet.

"Would the dust on Mars be made from Iron and if so, is it magnetic?"

The dust on Mars is what gives it the red color and on Earth this is typical of iron minerals within rocks coming into contact with oxygen and oxidising (this is the same effect as rust!). So, we believe that perhaps iron, or iron oxides, may be in the dust on Mars.

One project (on Pathfinder) tried to test how strong the magnetism of the dust was and there is at least some magnetic material floating in the atmosphere. There have been suggestions that the presence of iron oxides may be due to water!

"Is the surface on Mars like Earth only without water?"

There are a number of similarities and differences between Mars and Earth. Starting with rock types: on Earth, basalt is the most common rock type and from the TES we believe that this is the most common rock on Mars also. Basalt is formed from volcanoes like we see in Hawaii and on the sea floor. Both Earth and Mars have volcanoes, lava flows, valleys (compare the Grand Canyon and Valles Marinaris). We see sand dunes on Mars and we think we see channels possibly formed by water also. There are ice caps at the poles on Mars and we have ice caps at both of our poles too. Impact craters are frequently seen on Mars and we know of craters on Earth but most of ours have been eroded and are hard to see.

The differences between us are that there are no plate tectonics on Mars (or at least we don't see any evidence of it), there have been suggestions that Mars had plate tectonics in the past but the planet cooled down until the plates no longer moved.

The features on Mars also seem to be much larger than those on Earth - this could be due to its lack of plate tectonics. Olympus Mons, Mars' largest volcano is 24 km (15 miles) high and more than 550 km (340 miles) wide!! Compare that with Everest which is 8.8 km(~5 miles)high.

Valles Marinaris would stretch from Los Angeles to New York City, which is several times larger than the Grand Canyon.

The shape of volcanoes on Mars are similar to shield volcanoes on Earth. Some voclano morphologies are unique to Mars, these are called Patera, which are very flat volcanoes whose flanks slope at about 3 degrees.

Mars shows a contrast between its northern and southern hemispheres - its northern hemisphere is low lying in comparison to its southern highlands. Mars also has many more and larger impact craters and this could also be due to the fact that Earth has plate tectonics and many lands that have been impacted may have been eroded by wind and rain.

Cheers,
Mr. Garry & Ms. Semple