Prac Two Flashcards
What is a chondrite?
Small meteorite containing ‘chondrules’ (round particles) that show that they formed in zero gravity.
What is an achondrite?
A meteorite that was once part of a planetismal or a planet. Formed by rounded particles melting together under the influence of gravity.
What is a Widmanstatten structre?
A mesh like distribution of a precipitating phase in a solid state transformation, which occurs along preferred crystal planes. Usually formed by rapid cooling and when the transforming phase has a large grain size.
Most iron meteorites have Widmanstatten patterns.
They are formed from the core of ancient planets that were destroied around 4.5 billion years ago.
These patterns can only be formed by interwoven bands of kamacite and taenite, which can only form over literally millions of years of very slow cooling
What is a fusion crust?
When the exterior of a metiorite is melted due to travelling at extreme seeds throught an atmosphere. When it slows down to the point where no more melting occurs, the last melt to form cools to make a think, glassy coaching called the fusion crust.
How could you tell a metiorite from a normal stone?
1) Does it have chondrals?
2) Does it have Widmanstatten patterns?
3) Does it have a fusion crust?
4) What is its chemical structure (iron or iron nickle).
If you were to build a layered planet like the Earth, out of metiorites, what metiorite would you use?
Core: Predominantly nickle and iron, thus could be made from iron metiorites.
Mantle: Predominantly iron, thus could be made from stoney iron metiorites.
Crust: Predominantly rocks and minerals, thus could be made from stoney metiorites.
How to the outer planets differ from the inner planets, with regards to their densities, equatorial diameters and atmospheres.
Outer gas giants:
Have lower densities (0.687-2.050 g/cm^3) and all contain hydrogen and helium. Have larger equatorial diameters (49528-142984 km).
Inner rocky planets:
Have higher densities (3.340-5.520 g/cm^3) and are composed of heavier elements. Have smaller equatorial diameters (3475-12756 km).
What evidence did atronomers working int he late 1800s and early 1900s used to prove that there was water and possible life of Mars?
In the late 1800s, astronomer Percival Lowell envisioned Mars as a planet laced with engineered waterways and canals. He derived his guess from observing narrow streaks on the surface of Mars through telescopes. Since straight lines don’t typically appear in nature, he surmised, then that they must have been made by intelligent life.
What was the view of scientists in the 1970s-90s about the presence of water and life on Mars?
It was believed that due to the eidence left by apparent water bed, that water did exsit on Mars, as recently as 100,000 years ago.
How has eviedence from the NASA Phoenix Lander (2008) and the rovers Spirit and Oppertunity (2004), and the rover Curiosity (2012) changed out views about the presence or absence of water on Mars?
There are ice caps known to contain frozen water (and frozen CO2). There is also traces of water vapour in the atmosphere.
