Moon Chemistry Confirms Violent Origin

The European Space Agency's lunar-orbiting craft called SMART-1 has completed the first detailed chemical mapping of the lunar surface. The detected chemicals, such as calcium and magnesium, give a boost to the longstanding theory that the Moon formed from the debris flung into space after a collision between early Earth and a Mars-size planet.

Calcium, in particular, is found deep inside Earth. So if the Moon has a lot of calcium, then perhaps it is made of material that was once inside our planet.

Armed with miniaturized instruments—including an ultra-compact electronic camera, an X-ray telescope the size of a toaster for mapping chemical composition, and high-tech communication gadgets—SMART-1 had lofty goals. It was to pin down out how the Moon came to exist, search for water locked up as ice in the depths of Sun-deprived craters, and map the mineral composition of the Moon's crust.

Prior to the Apollo missions, there was no consensus among planetary scientists regarding the Moon's formation. One theory claimed that the Earth and the Moon formed at the same time from the same disk of swirling dust and gas, while another purported that the Moon is a scoop of Earth that split off in the early stages of our solar system.

Besides sending home awe-inspiring photos, the Apollo missions delivered 842 pounds (382 kilograms) of lunar rocks and soil—the first pieces of chemical evidence to help explain the Moon's formation.

The favored theory now describes a violent collision between the Earth and a planet-size object, which hurled molten rocks and dust from both contenders into space. Over time, the debris congealed into the Moon.

With most Moon know-how coming from Apollo’s six landing sites, scientists saw lots of room for error. To solve the lunar-forming puzzle, a global investigation of the entire surface was needed.

Enter SMART-1 (Small Missions for Advanced Research and Technology), a spacecraft equipped with seven high-tech instruments that would give a detailed map of both chemical make-up and topography over the Moon’s entire surface.

One of the most important devices, D-CIXS (pronounced dee-kicks) recorded hours of X-ray data. When the Sun’s rays hit the Moon, the X-rays caused atoms to fluoresce and emit their own X-rays. The D-CIXS (Demonstration Compact Imaging X-ray Spectrometer) telescope translated the amount of energy released into the type and abundance of different elements.

D-CIXS detected the major components of rocks: aluminum, silicon, magnesium, and calcium. However, elements like calcium are not homogenously mixed throughout the Moon. To paint a three-dimensional picture of the chemical composition, planetary scientists needed both surface and “bulk” data.

What the project team is calling a cosmic coincidence helped to land that information. On January 2005, a massive solar flare flooded the Moon with X-rays. Meanwhile, the craft was peering over a region called Mare Crisium—the same location in which Russian Landers had collected soil samples in the 1970s. There, the spectrometer detected calcium in similar amounts to the data collected by the landers.

Plus, calcium showed up in broad areas across the entire lunar surface. This rock-building element lends support to the impact theory.

"From SMART-1 observations of previous landing sites we can compare orbital observations to the ground truth and expand from the local to global views of the Moon," says Bernard Foing, Project Scientist for SMART-1.

"We have good maps of iron across the lunar surface. Now we can look forward to making maps of the other elements," said Manuel Grande of the University of Wales and D-CIXS' Principal Investigator.

Since the Moon’s rotation around its axis is equal to its orbital period, or the time it takes the Moon to travel around Earth, the same side always faces Earth. While scientists have studied samples from the Moon’s near side, the far side and its polar regions have remained in the dark.

For instance, the lunar south pole sits in the solar system’s largest crater, called the South Pole-Aitken Basin, which is 1,616 miles (2,600 kilometers) across and 7.5 miles (12 kilometers) deep. SMART-1 snapped loads of photos of the crater, while gathering chemical data. With such depths, the scientists hope to get a peek at the Moon’s mantle layer, just beneath the crust. Since the Moon accreted material over time, the deeper you go the further back in time you go.

This September, the craft’s nearly three-year mission will come to an end with a fiery crash.

As the craft nears shut-eye, its instruments will keep all eyes on the Lake of Excellence, a volcanic plain area surrounded by highlands in the mid-southern latitudes. Such close capture should give scientists insights into the formation of this region.

But in this case Pluto is at fault, It crossed Uranus's orbit! If you let it get away with that, no telling what Pluto will do to Uranus. Might just try to poke it!

Remember, eccentricity is not inclination. You are getting your terms mixed up.

The eccentricity of our planet's orbit is mild; aphelion and perihelion differ from the mean Sun-Earth distance by less than 2%. In fact, if you drew Earth's orbit on a sheet of paper it would be difficult to distinguish from a perfect circle and that is with e = 0.0167. As for a perfect circle, there never will be a perfect circle with the orbital elements. Remember the other planets are also "tugging" on each other.

And indeed tidal lock is the reason the Moon keeps one side to the Earth.

As I said previously, The Earth's rotation is slowing down as well.

We see a number of tidally locked systems within the solar system. Often this invloves more than two bodies.

A more in depth discussion of tidal locking since the Moon is tidal locked to the Earth. The reason the Moon keeps one face to the Earth (Its rotation on its axis matches the period of its orbit) is it is tidally locked to the Earth. Here is a more in depth explanation. The total angular momentum of the earth moon system, which is spin angular momentum plus the orbital angular momentum, is constant. (The Sun plays apart also) Friction of the oceans caused by the tides is causing the Earth to slow down a tiny bit each year. This is approximately two milliseconds per century causing the moon to recede by about 3.7 centimeters per year. As the Earth slows down, the Moon must recede to keep the total angular momentum a constant. In other words as the spin angular momentum of the earth decreases, the lunar orbital angular momentum must increase. Here is an interesting side note. The velocity of the moon will slow down as the orbit increases.

Another example of tidal locking is the orbit period and rotation of the planet Mercury. What is interesting about this one is that instead of a 1:1 synchronization where Mercury would keep one face to the Sun at all times, it is actually in a 2/3:1 synchronization. This is due to the High eccentricity of its orbit.

There also can be more than one body “locked” to each other. Lets take a look at the moon Io. Io is very nearly the same size as the Earth’s moon. It is approximately 1.04 times the size of the moon. There is a resonance between Io, Ganymede, and Europa. Io completes four revolutions for every one of Ganymede and two of Europa. This is due to a Laplace Resonance phenomenon. A Laplace Resonance is when more than two bodies are forced into a minimum energy configuration.

There are also examples of tidal locking in the asteroid belt.

First, the asteroid belt has an estimated total combined mass of less than 1 tenth of the Earth's moon. Second, Jupiter has a profound effect on the asteroid belt.

Since Jupiter has a semimajor axis of 5.2 AU (I AU is the distance from the Sun to the Earth) it ends up with an orbital period of 11.86 years. Since the asteroids are not all at the same distance from the sun, there orbital periods will differ in a direct relationship to their distance from the sun. This will result in some of them having an orbital period of one half of Jupiter. This puts those particular asteroids in a 2:1 orbital resonance with Jupiter. The result of this resonance is gaps called Kirkwood's gaps. The rub is why did not this asteroid belt form a small planet? The reason is the gravitational force of Jupiter. It perturbs the asteroids giving them random velocities relative to each other.

Another effect of both Jupiter and the Sun on the asteroid belt is a group of asteroids that both precede and follow Jupiter in its orbit by 60 degrees. These asteroids are known as the Trojans.

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