Tuesday, July 15, 2014
PHOBOS AND DEIMOS – MARTIAN MOONS
There are two small asteroid-like moons that orbit Mars: Phobos and Deimos. Both are named after ancient Greek gods. The larger moon, Phobos, passes across the Martian sky from west to east three times in one Martian day (one sol). On Mars it would appear as half the size of a full moon on Earth. It is so close to the surface that it would not be visible from the Martian poles.
Deimos orbits at about 12,470 miles from the planet and moves slowly from east to west. This moon takes about 30 hours, a little over one Martian sol, to orbit its host. Because of its distance from the planet and the fact that it is only 8 miles across, it appears as a small dot of light in the sky, more like a star than a moon. The surface of this moon is covered with a layer of powdery dust that could be several hundred feet deep. Only the tips of giant boulders can be seen peeking above the dust. Scientists believe the dust formed as a result of billions of years of meteorite impacts.
Phobos is the larger of the two moons at 14 miles across, and it orbits Mars from only 3,700 miles from the surface of the planet. Phobos is interesting because of its grooves and distinctive crater. It is believed that Phobos survived a powerful impact that may have fractured its interior. The impact may also be responsible for a series of long, deep grooves that appear to radiate away from the crater to an oddly shaped area on the other side of the moon. This impact gouged a large crater which has been named the Stickney crater. Asaph Hall discovered the moons in 1877. He named the crater on Phobos “Stickney,” his wife’s maiden name. He said if it were not for her encouragement he would have given up his search for the Martian moons.
Scientists can only speculate if these moons were born of Mars itself or if they are captured meteors, though the more popular belief is the latter. Much like our Earth moon, both Martian moons always face the same side to the planet. Both moons were named after the sons of Aries, the Greek god to Mars. Phobos means “fear” and Deimos means “dread.” Deimos seems to be slowly spiraling away from the planet while Phobos is drawing closer, which may cause it to collide with the planet in about 50 million years.
I’m wondering: Will Deimos disintegrate and form a ring around Mars before it would collide? Scientists believe there may be water on Phobos; if so, will we create a base on Phobos to store supplies? What do you think will happen?
Visit this link for images of Phobos and Deimos:
My resources are: NASA, Starry Skies, Universe Today, and Space.com
Discover my Lill and Mewe series books about Mars on my website: www.authorjeanelane.com
Wednesday, July 2, 2014
OORT CLOUD - IS THIS REALLY A CLOUD?
The Oort Cloud is not really a cloud at all but if we could ‘see’ it from a distance it may have that appearance. It has yet to be observed, the Oort Cloud is a spherical collection of icy objects presumed to exist in the far reaches of the Solar System. It was first suggested by Jan Hendrik Oort in 1950, after his observations of comets. He concluded that comets had the following things in common:
· Their orbits indicated that they did not originate in interstellar space.
· They come from all directions – there is no single orbit.
· Their aphelia (farthest point) tended to group at about 50,000AU (the sun is 1AU from Earth).
Taking all of these observations into consideration and the frequency that they occurred, Oort decided that billions of potential comet material must exist in a spherical shell surrounding the Solar System. Then given their distance from the sun and the weaker gravitational pull, disturbances from objects outside the Solar System could ‘knock’ these icy objects into plunging orbits around the Sun. This would result in the comets we observe.
The Oort Cloud is still generally acknowledged as the origin of the long-period comets, whereas the short-period comets originate from the Kuiper Belt. The Oort Cloud is thought to be an extension of the Kuiper Belt only much larger, containing billions of objects and maybe trillions of small icy objects. Scientists believe that during the planetary formation these objects were left-over debris. They were caught and flung out to the edge of the Solar System by the gravitational pull of Jupiter and Saturn, acting like a sling shot.
Two of the most famous comets, Halley and Swift-Tuttle, possibly higher orbit comets are ones that were pulled into shorter period orbits by the planets. Long period comets, such as Hyakutake and Hale-Bopp can appear at any time and come from any direction, but these two bright comets can usually be seen every 5 to 10 years.
We still have much to learn about the Oort Cloud. To date, scientists believe this region may contain the existence of two Oort Clouds, the inner and the outer clouds. They believe that the objects that reside there formed closer to the sun and were scattered to the outer regions due to gravitational effects. The last theory most commonly accepted is that the Oort Cloud defines the outer most region of our Solar System under the influence of the gravitational pull of our sun.
Let’s take a look – Images and a video:
My sources: Kids Astronomy, Wikipedia, Solarviews.com, Space.com, European Space Agency, Astronomy/Cosmos, and Universe Today.