Chp 9: Mercury Flashcards
Why is it hard for us to view Mercury’s surface?
it always stays in the same region of the sky as the Sun
(which makes it hard to see from Earth), and it never gets closer to us than about 80 million kilometres.
How is Mercury similar to the Moon? How do their surfaces differ?
- for both, rotation has been altered by tidal attraction, their surfaces are heavily cratered, their large craters are flooded by ancient lava flows, and both are small, airless and have ancient, inactive surfaces.
- Unlike the Moon, Mercury has enormous cliffs that are hundreds of km long and are thought to be fault systems.
What mission/craft provided us with the most information about Mercury?
the MESSENGER mission.
Which is longer, a day or a year on Mercury?
- A day is longer, one full Mercury day is two Mercury years long.
- a Mercury year 88 Earth days and a solar day 176 Earth days.
Is the surface of Mercury hot or cold? Why?
-temperature variations on Mercury are the most extreme in the Solar System. At perihelion (the point in its orbit when it is closest to the Sun), Mercury is only 46 million km away from the Sun, but at aphelion (the point in its orbit when it is furthest from the Sun), it is 70 million km away. That orbit, together with the fact that the days are so long on Mercury, and because it’s too small to keep an atmosphere. means that temperature variations on Mercury are the most extreme in the Solar System, ranging from +427°C at full-sunshine to -173°C at night.
What is the origin on the atmosphere on Mercury?
- Mercury actually has a very thin atmosphere consisting of atoms blasted off its surface by the solar wind.
- properly called an exosphere.
What is the evidence for lava flows on Mercury?
Mercury has enormous cliffs that are hundreds of km long and are thought to be fault systems. Smooth plains (volcanic deposits) cover approximately 40% of the surface, some appearing to be a result of explosive eruptions.
Why does Mercury have a low albedo?
carbon deposits - remains of material from cometary impacts - could account for Mercury’s low albedo.
Since there are no plate tectonics on Mercury why do we see things like faults and scarps?
These features were likely caused by shrinkage: it’s estimated that as Mercury cooled, its diameter has decreased by at least 10 km. Imagine the wrinkled skin that develops on a raisin as a grape dries, and you have a mental picture of how the surface of Mercury has been affected by shrinkage.
How are hollows formed? (Mercury)
“hollows”, which are pits in the surface, thought to be formed when material beneath the surface was vapourised away after asteroid impacts. That would require unexpectedly high concentrations of volatile (i.e., easily vapourised) elements in Mercury’s crust.
albedo
We use the term albedo to describe the proportion of light that gets reflected by a planetary body
How does the interior of Mercury compare with Earth’s?
Mercury is denser than any other planet except Earth. Because Mercury’s surface appears to be normal rock, its interior contains a large core of dense metals.
What is the geological history of Mercury?
- Stage 1: Mercury formed in the innermost part of the solar nebula, and, as we have seen, a giant impact may have robbed it of some of its lower-density rock and left it a small, dense world with a large metallic core
- Stage 2: Mercury suffered heavy cratering by debris in the young Solar System.
-Stage 3: flooding, began with lava flows filling some lowlands. The Caloris impact may have been so big it fractured the crust and triggered still more
outpourings of molten lava. These later lava flows formed the smooth plains. the age of lava flooding ended quickly, perhaps because the shrinkage of the planet squeezed off the lava channels to the surface.
-Stage 4: slow surface evolution, is now limited to micrometeorites, which grind the surface to dust; rare, larger meteorites, which leave bright-rayed craters; and the slow but intense cycle of heat and cold, which weakens the rock at the surface. The planet’s crust is now thick, and although its core may be partially molten.
What two elements are surprisingly common on the surface of Mercury?
sulphur and magnesium
Is there water on the surface of Mercury? How do we know? Why hasn’t the heat of the Sun evaporated it?
Spectrometers on MESSENGER measured high levels of hydrogen at Mercury’s north pole suggest the material is water-ice at least 10-30 cm thick. In addition, reflectance measurements of this area match those expected for water-ice.
-Mercury’s rotational axis is less than 1° from the ecliptic (the orbital plane), which means that there are areas that are never exposed to sunlight. These areas can have temperatures below -150 °C!
