Planet data; Gaia

SOLAR-PLANET DATA

A Gaian system may exist on 3 other bodies in the Solar System: Mars, Europa, & Titan.

and Skip down to "PLANETISIMALS".
Skip down to "KBOs".
Skip down to "MOONS".
.
THE NINE SOLAR PLANETS:

1: MERCURY data (averages):
. . Diameter: 4,878 km
. . Time to rotate: 58.6 days
. . Orbit: 88 Earth days

Compared to Earth:
. . Mass: 5.5% of Earth's
. . Diameter: 38% of Earth's
. . Distance from Sun: .47 AU
. . Temperatures fluctuate from 750 degrees F during the day, to -320 F at night.

2: VENUS data (averages):
. . Diameter: 12,104 km
. . Time to rotate: 241 days
. . Orbit: 225 Earth days

Compared to earth:
. . Mass: 82% of Earth's
. . Diameter: 95% of Earth's
. . Distance from Sun: .7 AU

Pressure from the dense atmosphere of sulfuric acid gas is about 95 times greater than Earth's.
. . Venus' orbit is the closest to a perfect circle. It is the only planet in the solar system whose day (241 Earth days) is longer than its year (225 Earth days).

3 & 4: LUNA data (averages):
. . Diameter: 3,476 km
. . Time to rotate: 27.3 days*
. . Orbit: 27.3 days*

Compared to Earth:
. . Mass: 1.2% of Earth's
. . Diameter: 27% of Earth's
. . Distance from Earth: 384,400
. . Travels around the Earth at 1.6 km per second.
. . Evidence of ice near the Moon's poles, perhaps as much as 6 billion tons of it.
. . Daytime temperatures on the sunny side reach 134 degrees C; on the dark side it gets as cold as -153 C.
. . As Luna orbits Earth, its gravity helps generate an ever-shifting tide (the Sun contributes to this, too) that goes around the planet. If you could draw a line from the center of Earth to the center of Luna, you’d see that the high tide facing Luna is actually just a bit ahead of Luna along this line. Why? Because Earth makes a full rotation on its axis just a bit faster than Luna is able to orbit the planet. Friction pushes the high tide ahead. The tide, in turn, has a tiny gravitational effect on Luna. It pulls the satellite forward and, according to the complex mechanics of orbiting objects, into a higher orbit. When it formed, Luna was about 22,530 km from Earth. It's now more than 450,000 km away. Some of Earth's rotational energy is stolen by Luna, causing our planet to slow down by about 1.5 milliseconds every century.
. . Luna's center of mass is not at its geometric center; it's about 2 km off-center. Its core is hot and perhaps partially molten, as is Earth's core. But data from NASA's Lunar Prospector spacecraft showed in 1999 that the Moon's core is small -- probably between 2 percent and 4 percent of its mass. This is tiny compared with Earth, in which the iron core makes up about 30 percent of the planet's mass.

The Earth-Luna distance is, on average, roughly 384,402 km. And astronomers know this to within about 2 cm. It's creeping away from us at about 2.5cm a year.
Luna is not a primordial object; it is an evolved terrestrial-type planet with internal structure similar to that of Earth. The youngest Moon rocks are virtually as old as the oldest Earth rocks. Moon rock ages range from about 3.2 billion years in the maria (dark, low basins) to nearly 4.6 billion years in the terrae (light, rugged highlands). The earliest processes and events that probably affected both planetary bodies can now only be found on Luna. The distinctively similar oxygen isotopic compositions of Lunar rocks and Earth rocks clearly show common ancestry.
. . Luna likely formed when a Mars-sized object hit a fully-formed Earth. The collision would have given Earth its spin, defined what we now call an equator, and put enough material into orbit at the right distance from Earth to allow the formation of a satellite. Luna is thought to have been pieced together by the bits that got blown off the upper layers of Earth, as well as the outer portions of the object that hit Earth. The shock of the impact stripped material from the outer layers of Earth and the impacting object. The mostly iron cores of both bodies melded into Earth's core. Demonstrations with simulations show that a single impact can give you an iron-depleted Moon of the right mass, the current mass of the Earth, and the current angular momentum of the Earth-Moon system.
. . All Lunar rocks originated through high-temperature processes with little or no involvement with water. They are roughly divisible into three types: basalts, anorthosites, and breccias. No sandstones, shales, or limestones. Early in its history, Luna was melted to great depths to form a "magma ocean." A magma ocean covered Luna to a depth of many tens of kilometers or more. The lunar highlands contain the remnants of early, low-density rocks that floated to the surface of the magma ocean. The lunar magma ocean was followed by a series of huge asteroid impacts that created basins which were later filled by lava flows. Volcanic fire fountains produced deposits of orange and emerald-green glass beads.
. . Its crust is thicker on the far side. Relative to its geometric center, Luna's center of mass is displaced toward Earth by several kilometers.
Aug, 01: Computer simulations gave new life to a theory that has intrigued astronomers for years: the idea that one big collision between the Earth and a Mars-sized planet gave birth to Luna. The so-called ``giant impact'' theory was first envisioned in the 1970s, but now scientists at the Southwest Research Institute and the University of California-Berkeley have put together a scenario that would account for the moon's creation as well as the fact that a day on Earth is 24 hours long.
. . An enormously energetic but oblique crash between Earth and a planet the size of Mars, which is about half Earth's size. The energy unleashed by this collision some 4.5 billion years ago would have been enough to destroy the incoming planet and melt Earth all the way through, Canup said. There would also have been some vaporized rock debris kicked up from the crash, which would start orbiting Earth.
. . "Once the orbiting debris cooled, it's from that stuff that the moon then coalesced", Canup said. The whole process, from collision to formation of the moon, took less than 100 years, she said -- an almost inconceivably short time in planetary terms.
. . The glancing angle of the collision --perhaps 40 degrees or so-- caused Earth to start spinning much faster than it does now, Canup said. In those early times, an Earth day would have lasted only five hours.
Luna is made up of material blasted off the surface of the proto-Earth. It's almost entirely covered with the aluminum-rich rock called anorthosite. Anorthosite forms when molten rock cools slowly and lightweight aluminum-rich minerals float to the top of the magma. The only known source of sufficient heat for such an event is very rapid accretion, as expected if the Moon formed as a result of a giant impact between Earth and a massive body.
. . The 2,600 kilometer-wide South Pole-Aitken basin is one place on the Moon that hints at the lunar heart of iron. The giant impact scar is on the far side of the Moon and all three missions verified that its surface is not covered with aluminum-based mineral, but instead displays a lot of ferrous compounds. Scientists have long thought that this happened when the impact ripped off the top layers of the moon then exposed iron from the core.
Luna is Earth's only natural companion. Right? Maybe not. In 1999, scientists found that a 5-km wide asteroid may be caught in Earth's gravitational grip, thereby becoming a satellite of our planet. Cruithne, as it is called, takes 770 years to complete a horseshoe-shaped orbit around Earth, the scientists say, and it will remain in a suspended state around Earth for at least 5,000 years.
. . Another is a co-orbital object, not a Moon, astronomers stress, but they are calling it a quasi-satellite of Earth. "They both go around the Sun in one year, which is why Earth can have a big effect on their orbits." Other space rocks have been found in similar orbits, including one called Cruithne.
The Earth's mass is about 5.98 x 10-X24 kg. (~6, w 24 zeroes)
The Earth has an average density of 5520 kg/m3 (water has a density of 1027 kg/ m3). Earth is the densest planet in our Solar System.
To escape the Earth's gravitational pull, an object must reach a velocity of 11,180 m/sec (24,840 mph).
The Earth revolves around the Sun at a speed of about 30 km/sec. This compares with the Earth's rotational speed of approximately 0.5 km/sec
78% nitrogen, 21% oxygen, 0.9% argon, 0.03% carbon dioxide

5: MARS: data(averages):
. . Diameter: 5,786 km
. . Time to rotate: 24 hours, 37 minutes
. . Orbit: 687 Earth days

Compared to Earth:
. . Mass: 11% of Earth's
. . Diameter: 53% of Earth's
. . Distance from sun: 1.5 AU

Until about [March 01], planetary astronomers believed that the southern cap contained nothing but frozen carbon dioxide, also known as dry ice. New research suggests otherwise: a thick sheet of carbon dioxide ice would be too soft to stay stable. "The thought now is that carbon dioxide ice is so weak that it would flow away, like a glacier, even at very low temperatures", Zuber explains. "So to maintain the topography of the south polar cap, there has to be water ice in there stiffening it up."
. . Zuber's results confirmed that the northern cap is composed entirely of water ice. Summer temperatures at the cap (which has an elevation several km lower than the southern cap) are high enough to vaporize frozen carbon dioxide.
. . 1200 km across, and up to 3 km thick, the northern cap has a volume just half that of the Greenland ice sheet. It contains no more than one tenth the amount of water needed to fill an ancient ocean. The northern cap lies at a lower elevation than the rest of the planet.
. . The air density at martian "sea level" is roughly equivalent to that of Earth's atmosphere at 70,000 feet altitude!

6: JUPITER data (averages):
. . Diameter: 142, 790 km
. . Time to rotate: 9 hours, 50 minutes
. . Orbit: 11.9 Earth years
. . Moons: 60+

Compared to Earth:
. . Mass: 317.8 times Earth's
. . Diameter: 11.2 times Earth's
. . Distance from Sun: 5.2 AU
. . Volume: 1,300 X the of Earth. It has a core of rock many times the mass of Earth.

7: SATURN data (averages):

Diameter: 129,534 km
. . Time to rotate: 10 hours, 39 minutes
. . Orbit: 29.5 years
. . Moons: 34-35

Compared to Earth:
. . Mass: 95 times Earth's
. . Diameter: 9.4 times Earth's
. . Distance from Sun: 9.6 AU

Saturn's ring particles range in size from microscopic dust to barn-sized boulders. If you assembled them all in one place, you would have only enough material to make one icy satellite 100 - 200 km wide. "A moon-sized object from the outer solar system might have flown nearby Saturn, where tidal forces ripped it apart. Or maybe an asteroid smashed one of Saturn's existing moons."
. . Ring particles range in size from microscopic dust to barn-sized boulders. It's 250,000 km wide, but only a few tens of meters thick. A sheet of paper the size of San Francisco would have about the same ratio of width to depth!
. . Theorists now agree that beyond Saturn, there was never enough material to build such planets using the crash-and-stick approach. Uranus and Neptune either formed closer in and migrated outward, or they were created by some other means.

Mimas is one of the innermost moons of Saturn. It has a low density, indicating that it probably consists largely of ice. Its surface is dominated by a 130 km-wide impact structure called Herschel crater. The crater is 10 km deep, with a central mountain almost as high as Mount Everest on Earth. The impact probably came close to destroying Mimas.
. . Because Mimas has such a low temperature, about -200C (-328F), scientists think the impact features may date back to the time of the moon's creation.
Sept 10, 04: UK scientists using the Cassini probe have found a new ring and one, possibly two, new objects orbiting Saturn. The known number of moons of Saturn rises to 34. Or 35. Scientists cannot yet definitively say if it is a moon or a temporary "clump". If it is a moon, its diameter is estimated to be 4-5 km and it is located 1,000km from the F-ring --Saturn's outermost ring.
Aug 16, 04: Two new moons were spotted around Saturn by the Cassini space probe. The new moons could be the smallest bodies there; approximately 3km and 4km across, and are located between the orbits of two other moons, Mimas and Enceladus.
Iapetus is 1,460 km (907 miles) wide and circles Saturn at a distance of about 3.6 million km (2.2 million miles). Like Earth's Moon, Iapetus' rotation and orbit are in lockstep, both taking 79 Earth-days.
. . The side of Iapetus that always faces forward as it moves along its orbital path -- think of the front of a race car on a circular track --reflects just 5% of the sunlight that hits it. The trailing hemisphere is much brighter, reflecting 50% of sunlight. The dark material on Iapetus seems also to be concentrated in the bottoms of some craters. The radar system sees Iapetus as a uniform object, meaning no difference between the light and dark sides. That could mean that on the dark side there is merely a thin coat of some darkening material over the ammonia-laden water ice, like an inch of dirt atop clean snow.

8: URANUS data (averages):
. . Diameter: 51,115 km
. . Time to rotate: 17 hours, 54 minutes
. . Orbit: 84 Earth years
. . Moons: 21

Compared to Earth:
. . Mass: 14.5 times Earth's
. . Diameter: 4.1 times Earth's
. . Distance from Sun: 19.2 AU
. . It orbits at an extreme tilt of 98 degrees.
. . Moons: 22. 10 so-called "regular" moons. The rest are "irregular" --those in off-plane & eccentric orbits.
. . Oct 28, 02: Astronomers announced the discovery of a new moon of Uranus, boosting the planet's tally of orbiting satellites to 21. The moon, unofficially called S/2001 U 1, is between 9 and 18 km across, and thought to be a remnant of an ancient collision when the solar system's planets first formed. The moon and five others circle Uranus in irregular, eccentric orbits. The 15 other moons orbit on the same plane.

9: NEPTUNE data (averages):
. . Diameter: 49,525 km
. . Time to rotate: 19 hours, 12 minutes
. . Orbit: 165 Earth years
. . Moons: 11, as of Jan 13, 03.

Compared to Earth:
. . Mass: 17.2 times Earth's
. . Diameter: 3.9 times Earth's
. . Distance from Sun: 30 AU
Neptune's constant gales have been clocked at 1,930 km per hour.

Oct 27, 00. Neptune is radiating heat at about 60 Kelvins (-212.8 C). Scientists calculate that Neptune would be only about 46.6 Kelvins (-226 C), if its only source of heat were sunlight.
. . The gas giant planets' main compositions are almost identical to that of the Sun --83 percent hydrogen, 15 percent helium and two percent methane. This means that helium hasn't sunk to the center of the planet, as some models had suggested, but has stayed mixed in the atmosphere.
. . Neptune's rings are made up of dust particles thought to have been made by tiny meteorites smashing into the moons.
. . ==========
. . The International Astronomical Union, the organization responsible for classifying planets, gives these reasons for questioning Pluto's status as a planet:

  1. All the other planets in the outer solar system are gaseous, giant planets; whereas Pluto is a small solid object.
  2. Pluto is smaller than any other planet by more than a factor of 2.
  3. Pluto's orbit is by far the most inclined with respect to the plane of the solar system, and also the most eccentric, with only the eccentricity of Mercury's orbit even coming close
  4. Pluto's orbit is the only planetary orbit which crosses that of another planet (during 1999 Pluto will again cross Neptune's orbit, thus regaining its status as the most distant planet)
  5. Pluto's satellite, Charon, is larger in proportion to its planet than any other satellite in the solar system.

. . So, for Pluto data, Skip down to "KBOs".
PLANETISIMALS
(incorrectly called "asteroids".)
A newfound 'tisimal companion brings the total number of known space-rock pairs to 31 --most are probably the result of collisions. Learning about binary 'tisimals in general would help scientists decide what to do if a pair of space rocks were ever found to be headed our way.
. . Seven pairs have been found beyond Neptune. One dancing duo is part of a special class of "Trojan" asteroids locked into orbits ahead of or behind Jupiter.
. . There are thought to be roughly 1,000 to 1,200 large NEOs (1 km or bigger) and hundreds of thousands of smaller ones. Some 16 percent of NEOs might be binary systems.
. . About a sixth of the discovered large planetisimals have moons. An international team used the Keck telescope on Mauna Kea, Hawaii, outfitted with adaptive optics, which allow astronomers to examine them, and other celestial objects, with unprecedented clarity. *
. . Each asteroid in one new pair is about 75 km across. They are separated by about 150 km, mutually orbiting a spot between. The asteroid pair was once assumed to be a single body, called Antiope, orbiting the sun in the outer parts of the asteroid belt between the orbits of Mars and Jupiter.
. . The team also found a small moon orbiting the large 'tisimal Pulcova, using adaptive optics on the Canada-France-Hawaii Telescope on Mauna Kea. Pulcova was the third asteroid observed to have a moon. The first was found in 1993 by the Galileo spacecraft, which observed a 1.5 km-wide moonlet around 30.5 km diameter Ida. The Merline team reported the second moonlet a year ago, circling the 200 km diameter Eugenia.
. . Eugenia, Pulcova, and Antiope are light bodies, with less density than rocks, even though their sufaces appear dark like rock.
. . The only other was found by a fly-by probe--Ida, diam 56 Km, moon, called Dactyl, 1.5 Km.

Eugenia stats: Diam: 201-215 Km. Year: 4.4 years. Day: 5.7 hrs. Distance from Sol: 2.7 A.U. (in the belt) Gravity: 1/270 G. or .0037G. Density (surprise) only 1.2 ! (rock is at least 3.0) So it's mostly ice, or is a rubble-pile with a lot of holes. Either way, it's mineable/habitable!

Its moon (unnamed yet): Diam: 13-15 Km. Distance from Eugenia: 1,190 Km.

Gravity on 34 km-long Eros is only about one thousandth of that on Earth. A human could easily jump off the surface. Tracking an orbiting spacecraft as it's tugged by Eros' gravity, the NEAR radio-science team calculated the asteroid's mass as 6,687 trillion kilograms. (6,687 billion tons, obviously)
. . It's about one-billionth the mass of the Earth. A 90-kilogram (200-pound) person on Earth would weigh about 28 grams (an ounce) on Eros. You could jump off it into space!
. . The measurements were used to calculate that Eros has a density 2.67 times greater than water, a bit lower than Earth's crust. That suggests Eros is not completely solid rock, but has surface rubble up to 330 feet (100 meters) thick, Zuber said.
. . The same spacecraft flew past 'tisimal 253 Mathilde --a big rubble pile-- in June 1997.
There’s at least ten thousand times as much surface area on the 'tisimals as on our home planet.
April 8, 02: A systematic survey of the 'tisimal belt, done in infrared wavelengths, indicates that there could be two or three times more large asteroids, those more than 1 kilometer (0.6 mile) in diameter, than had been thought. The infrared survey is better able to spot dark asteroids that might be missed by optical telescopes. About about 700,000 asteroids bigger than 1 kilometer.
. . Based on observations of portions of the main asteroid belt, between Mars and Jupiter, the new study estimates there are between 1.1 million and 1.9 million of these large space rocks. Many millions or perhaps billions of smaller asteroids travel around the Sun in the same belt.
. . Ceres has a surface that contains water-bearing minerals. It may hold a very weak atmosphere and frost, scientists say. Vesta, on the other hand, is thought to be dry, having been resurfaced by lava flows. It may have had an early magma ocean like Earth's Moon, researchers think.
Oct 16, 01: The official asteroid tally is 29,074. About 1,000 objects enter the books each month. The tally is expected to double in a matter of months and likely soar a startling six-fold or more within 3 years. And these are just the well-studied rocks. Roughly 150,000 more have been spotted but need further study before their orbits can be known well enough to put them in the books. Millions of small asteroids are thought to exist.

A comparison of Earth, Luna, Pluto, Quaoar.

KBOs: Some have companions orbiting around them. A total of seven is known so far, tho they're hard to find. That's 1 percent of all known KBOs. Many of the KBOs already found could be binaries, but with separations that we cannot as yet resolve with our limited telescopes. Like Pluto, many other KBOs orbit the sun in a 3:2 resonance with Neptune. Astronomers estimate that there are at least 35,000 Kuiper (KOY-per) Belt objects greater than 100 km in diameter --some may be bigger than Pluto. It contains as many as 10 billion objects at least 1.5 km across; astronomers estimate five to 10 of those are jumbo-size. Over the last decade, more than 500 Kuiper Belt objects have been detected.

There could be over a hundred thousand Kuiper-Belt Objects (KBOs) whose mass in total (not counting Pluto) would equal about 10% of the Earth's mass. The diameter of 2000 WR106 is estimated at between 531 to 1,207 km. Pluto is 2,365 km in diameter. The largest known asteroid, Ceres, is 917 km across.
KBO's have been found in three types of orbit. Main Belt KBO's, KBO's in a so-called resonant orbit with the planet Neptune, and SKBO's that have been flung into deep space after a gravitational encounter with Neptune. It is the most distant solar system object ever photographed, being 60 times further away from the Sun than the Earth. One of the others, 1999 CF119, has the largest known orbit of anything orbiting the Sun. Its furthest point from the Sun is 200 Astronomical Units (AU).

King of the Kuiper Belt.

PLUTO: Diameter: 2,301 km
. . Time to rotate: 6 days, 9 hours (same as Charon's orbit)
. . Orbit: 248 Earth years

Compared to Earth:
. . Mass: 0.2% of Earth's
. . Diameter: 18% of Earth's
. . Distance from sun: 39 AU
. . PLUTO has just 1/500 of Earth's mass, & appears to be simply the largest of an estimated 70,000 observable objects thought to lie between 30 and 50 astronomical units of the Sun.
. . Yet Pluto is at least 10 times more massive than the largest asteroid, 1 Ceres, and it dwarfs all known Kuiper Belt finds. Moreover, it has an atmosphere and a substantial moon. One suggestion with many adherents is that anything large enough to shape itself into a sphere should be a planet --a qualification satisfied by Pluto, but also by big asteroids like Ceres.

PLUTO's density, size and surface composition are strikingly similar to those of Neptune's largest satellite, Triton. It is probably a mixture of 70% rock and 30% water ice, much like Triton. One of the great surprises of Voyager 2's exploration of the Neptune system was the discovery of ongoing, vigorous volcanic activity on Triton. Will Pluto also display such activity?
. . Pluto's bright areas are a frosty mixture of nitrogen, methane and carbon monoxide. A weak signature of water was also spotted. But no one has been able to discern what makes up the dark areas. They may be an overlying layer of more complex molecules. (Like Charon?) Astronomers have detected frozen ethane on the surface of Pluto. The ethane is dissolved in a bed of nitrogen ice that covers much of Pluto's surface at a temperature of -233 degrees C.
. . Earth's atmosphere contains only one gas (water vapor) that regularly undergoes phase transitions between solid and gaseous states, but Pluto's atmosphere contains three: nitrogen, carbon monoxide and methane, like a comet's. Most of the molecules in the upper atmosphere have enough thermal energy to escape the planet's gravity. The gravity on the surface is about 7% of what it is on Earth.
. . The current temperature on Pluto varies by about 50 percent across its surface. The surface temperature on Pluto varies between about -235 and -210 C (38 to 63 K) This will get even lower as it moves farther from the sun.
Pluto is smaller than six of the solar system's moons (Io, Europa, Ganymede, Callisto, Titan and Triton) and Luna.
. . orbit: 5,913,520,000 km (39.5 AU) from the Sun (average)
. . diameter: 2274 km
. . mass: 1.27e22 kg
Pluto is the second most contrasty body in the Solar System (after Iapetus).
. . Pluto rotates in the opposite direction from most of the other planets.
. . Pluto is locked in a 3:2 resonance with Neptune; i.e. Pluto's orbital period is exactly 1.5 times longer than Neptune's.
. . Like Uranus, the plane of Pluto's equator is at almost a right angle to the plane of its orbit. (so does Charon orbit in that same plane? Yes. That speaks against any capture theory, tho it would slowly move to that plane in any event.)
CHARON ( "KAIR en" ) is Pluto's only known satellite:
. . orbit: 19,640 km from Pluto
. . diameter: 1172 km
. . mass: 1.90e21 kg
Pluto and Charon are also unique in that not only does Charon rotate synchronously, but Pluto does, too: they both keep the same face toward one another.
. . Its low density (about 2 gm/cm3) indicates that it may be similar to Saturn's icy moons (i.e. Rhea). Its surface seems to be covered with water ice. Interestingly, this is quite different from Pluto.
. . Charon may've once had a heat-source. It is composed predominantly of water ice at the surface-- but a form of ice that shouldn't exist at the frigid -225 C that is thought to be the hottest temperature the moon ever reaches. The ice appears to be in a crystalline form: its molecules are neatly ordered and arranged into the hexagonal crystals that water naturally forms when it freezes, rather than a random, broken down state that scientists call "amorphous."
. . Unique spectral features indicate that Charon's surface is made of about 25 percent ammonia and ammonia hydrate --substances which might be evidence for volcanism on Charon. This is surprising because at cold temperatures in the depths of the solar system, ultraviolet radiation breaks down the neatly arranged crystalline structure, leaving ice in a random, broken down state that scientists call "amorphous." At temperatures above -150 Celsius or so, ice becomes crystalline on its own, but most scientists have thought Charon must have been so cold for so long, that its ice should all be amorphous.
At half the size of Pluto, Quaoar --pronounced KWAH-o-ar -- is a large celestial object, but not large enough to be a planet. This is by far the largest they have discovered. It's about the size of all the asteroids put together.
. . Circling the Sun once every 288 years, Quaoar is located 1.5 billion km beyond Pluto. Quaoar has a highly regular orbit, tilted only about 7.9 percent. Faint ultraviolet radiation over the ages has slowly changed the surface of this rock-and-ice object to a dark, tar-like substance.
Nov 19, 01: 2001 KX76, a distant object located outside the orbit of Pluto in a region known as the Kuiper Belt. The use of virtual astronomy, researchers said, allowed investigators to study the rock's orbit over a longer period of time, and calculate a new diameter of 1,200 km or more.
Ceres was the first asteroid discovered, in 1801. It is big and relatively close, which is why it was found first. It is roughly 950 km wide.
. . The diameters of distant space rocks won't be known with certainty until future space-based observatories are devoted to accurately measuring their albedos. Under one assumption about the object's reflectivity (albedo), 2001 KX76 is probably 1,270 km in diameter, making it 66 larger across than Charon and even bigger than Ceres.
. . The truth is that 2001 KX76 could be a bit smaller than Charon. It all depends on how reflective such objects are. For instance, earlier this year, a Kuiper Belt Object (KBO) called 20000 Varuna was announced with an estimated diameter of 900 km. They compared the sunlight reflected from Varuna with its emission of heat, created by the solar energy that Varuna absorbs. The combination allowed them to calculate an albedo of 7 percent.
. . Applying this albedo to 2001 KX76 gives it a diameter of only 960 km.
. . Available evidence suggests that the newly discovered KBO may be in an orbital resonance with Neptune, orbiting the Sun three times for each time that Neptune completes four orbits.
. . The object has a distinctly reddish color typical of many primitive bodies in the outer Solar System. It's currently 6.4 billion kilometers from the Sun. Its orbit is inclined by approximately 20 degrees from the orbital plane of the major planets, but the detailed shape of its orbit remains uncertain.

MOONS

. . 02 Mars
. . 52 Jupiter
. . 30 Saturn
. . 21 Uranus
. . 08 Neptune
. . 100 TOTAL
Mercury, Venus, Earth, & Luna have no moons.
Like Mars' other moon, Deimos, Phobos has a thick layer of regolith, or dust and rock. It is thought to be especially thick on Phobos --up to 100 meters (330 feet). From Mars, Phobos would appear about one-third as big as Earth's moon. Phobos is getting closer to Mars every day. In about 50 million years, it will either crash into Mars or be torn apart by gravity. Shreds of Phobos might then form a ring around Mars, similar to the rings of Saturn.
. . Deimos is the smaller and more distant of the two Martian moons, with an average diameter of 13 km and an orbit that is 120,000 kilometers away, on average. On the surface of Deimos, the gravity is less than 0.1 percent that of Earth.

JUPITER'S

  1. Metis is the closest moon to the surface of Jupiter, and can be found within the main ring.
  2. Adrastea
  3. Amalthea
  4. Thebe
  5. Io is the third largest
  6. Europa
  7. Ganymede is the largest of Jupiter's moons, larger than Mercury.
  8. Callisto is the second largest.
  9. Leda, the smallest.
  10. Himaila
  11. Lysithea
  12. Elara
  13. Ananke
  14. Carme
  15. Pasiphae
  16. Sinope
Mar 10, 03: And on it goes.... The tally of Jovian moons has soared to 52 with the discovery of four small moons added to eight that were previously revealed last week. Included in the latest batch are two rocks estimated to be just 1 km in diameter. These are the first Jovian satellites calculated to be less than 2 kilometers. Jupiter has 29 moons that are no more than 4 km wide and several more that aren't much bigger. These small satellites are thought to be captured asteroids or chunks of larger objects that broke apart, though their exact origins have not been determined. Many of them orbit in a direction opposite the planet's rotation.
. . They now estimates that Jupiter might have 100 satellites down to the 1-kilometer range, though he stresses that this is just a guess. Countless smaller rocks and bits of dust are in the planet's gravitational clutches.
. . No other planet has more known satellites. Saturn has 30, Uranus 21 and Neptune 11.
Dec 18, 02: The International Astronomical Union announced a find which brings Jupiter's current moon count to 40. Currently designated S/2002 J1, the newfound moon is a tiny thing — only about 3 km wide.
. . S/2002 J1 is "irregular," meaning its orbit is large, eccentric, and inclined relative to Jupiter's equator. "Its orbit is very similar to the other known outer retrograde satellites," Sheppard told Astronomy.com. It orbits between the outer satellites Pasiphae (discovered in 1908) and the recently named Megaclite (discovered in 2000) at an average distance of 23.8 million km from Jupiter. Its orbit is inclined 163 degrees, and the moon takes 748.5 days to go around Jupiter once.
May 16, 02: Jupiter has 11 more moons than astronomers once thought, bringing the known total for the giant planet to 39, the most in our solar system. The small ones all have retrograde orbits and diameters between 2-5 Km. Of the 39, 31 are irregulars. Saturn, at last count, has 30. Solar System total: 73, plus Uranus & Neptune. Creepin' up on a hundred!

EUROPA: Tidal heating could provide sufficient energy to maintain an ocean of liquid water beneath Europa’s icy surface that is greater in volume than all the oceans of Earth combined!
. . Like each of the Galilean moons, Europa is spin-locked to Jupiter, rotating about its pole with a period identical to its orbital period of 3.6 Earth days. Europa is in a 1:2:4 resonance with Ganymede and Io --for every two times that Europa orbits Jupiter, Ganymede orbits once, and Io orbits four times. These simple ratios allow the satellites to line up every few days or so. Callisto does not participate in the resonance with the other three Galilean satellites, and its surface resembles Earth’s Moon --it is an old, cratered body with few, if any, signs of geologic activity.
. . Galileo spacecraft sensors indicate that the crust of ice covering the liquid ocean is 18K thick.
. . It's in a deadly radiation belt around Jupiter. Even a well-shielded human being on the surface of Europa, would still die in about 10 minutes. If you got beneath about 2 meters of ice, you’ll be okay.

Europa's magnetic field has now been measured --its strength consistent with an ocean 100 kilometers deep with a salt content about equal to that of the ocean on Earth.

Conjecture: "Organisms might be carried on a slow ride from the bottom to the top of Europa's icy crust. Sampling the surface composition may provide direct insights into the nature of the ocean deep below." He added: "Europa acts like a planetary lava lamp, carrying material from near the surface down to the ocean, and, if they exist, potentially transporting organisms from the ocean up toward the surface.
12-17-00. The Hubble Space Telescope has found an extremely tenuous atmosphere of molecular oxygen on Jupiter's second moon, Europa. The oxygen atmosphere is so tenuous that its surface pressure is barely one hundred billionth that of the Earth.
. . But it could easily be produced by purely non-biological processes. It's icy surface is exposed to sunlight and is impacted by dust and charged particles trapped within Jupiter's intense magnetic field. These processes cause the frozen water ice on the surface to produce water vapor as well as atomic H & O. The relatively lightweight hydrogen gas escapes into space, while the heavier oxygen molecules accumulate to form an atmosphere which may extend 200 kilometers above the surface.
. . Only three other satellites are known to have atmospheres: Jupiter's volcanically active moon Io (sulfur dioxide), Saturn's largest moon Titan (nitrogen/methane; by far the heaviest) and Neptune's largest moon Triton (nitrogen/methane).
. . Europa is the smoothest object in the solar system. The satellite has a mostly flat surface, with nothing exceeding 1 km in height. The surface of Europa is also very bright, about 5 times brighter than our Moon.
. . The inner core of Europa is suspected to be iron-sulfur, similar to that of Io. Since Europa has a lower density than Io (3.01 gm/cm?3), the size of the inner core is expected to be smaller than Io's.
. . Theory: Periodic tidal stresses form a network of fissures in the ice, which can open and close by about a meter. When a crack opens, water will rise 90 per cent of the way to the surface, Greenberg says. [less if the ice contains a lot of gasses.]
. . At the top of the fissures, ice both freezes and evaporates into the near vacuum. When the walls close again, they squeeze slush to the top, where it freezes. The cyclic flow of water up and down the cracks continually mixes the liquid.
. . The connection to the surface is vital. Here, solar radiation can split molecules, producing chemicals that could supply energy for life. What's more, enough sunlight might reach the upper few meters to drive photosynthesis. "You could have organisms a meter down, with roots hanging onto the cracks, unfolding their little leaves," says Greenberg. "If there were life in the cracks, the whole crack would be filled, it's such a hospitable setting."
12-17-00. Also, NASA's Galileo spacecraft has detected an ocean deep below the frozen crust of Ganymede, making it the third of Jupiter's moons thought to harbor liquid water beneath its surface.
. . Galileo scientists reported that a salty ocean capped by perhaps 170 km of ice. Images of the moon show an icy surface surprisingly dominated by faulting and fracturing, consistent with tectonic activity. Furthermore, recent study of the salt minerals that splotch Ganymede's mottled surface suggests that sometime in the remote past, briny water may have breached the ice.
. . Ganymede's deep-seated ocean today presents far less of a likely place to go prospecting for life.
. . Callisto may also hold an underground ocean. The ice surface must be so thick, as much as 150 km, that the minimal heat from within would never smooth out the surface.
IO (eye'-oh) , about the size of Luna, features mountains up to 16,764 meters tall. (The summit of Mt. Everest reaches a meager 8,839 meters. Io's surface is dotted with active volcanoes spewing plumes of sulfurous gas and emitting vast streams of scorching lava. The heat released from Io-- from lavas as hot as 1,800 Kelvin or 2,800 degrees Fahrenheit (1,528 degrees Celsius) -- is about 25 to 30 times greater per square foot than the heat released from Earth.
IO'S COLORS. The black spots are made of rock. White areas on Io have been confirmed to be sulfur dioxide frost. Red & green materials consist of sulfur compounds, "but we can't rule out other possibilities like green silicates." White: sulphur dioxide.
. . Mountains tower some 16 km above the surface. The highest point on Earth is Mt. Everest, in the Himalayas at 8.8 km. Io's mountains are not created in chains, as they often are on Earth, but are evenly distributed around the moon. And, surprise, they do not appear to be created by volcanoes. They might be built when large blocks of surface crust crunch together and are pushed up by the heat below. The blocks are seen as floating over a "mushy ocean" of magma, and over time, might collapse.

SATURN'S

  1. Pan is the closest known moon to Saturn's surface.
  2. Atlas orbits Saturn just to the side of the A Ring. This makes Atlas a shepherd moon.
  3. Prometheus
  4. Pandora, The outer shepherd moon of the F Ring.
  5. Epimetheus was confused with Janus, another of Saturn's moons. They actually trade places in each other's orbits every 4 years.
  6. Janus
  7. Mimas
  8. Enceladus has the highest albedo in the Solar System.
  9. Tethys is almost pure water ice.
  10. Telesto is one of the smallest moons.
  11. Calypso is one of the smallest moons.
  12. Dione is the densest of Saturn's moons.
  13. Helene
  14. Rhea is the second largest.
  15. Titan --largest.
  16. Hyperion is the largest object in the Solar System that is not spherical. It might have been part of a larger moon, which collided with something & broke.
Titan's surface appears to consist of several large lakes or seas separated by continents. The Cassini spacecraft will drop a sophisticated probe into Titan's atmosphere when it arrives at Saturn in 2004.
One of Saturn's rings, called the F-ring, is confined by two shepherding moons. Pandora rides herd on the outside, and Prometheus takes charge from within.
Iapetus is made up almost entirely of water ice. Most of Saturn's moons orbit the planet on the same plane, that of the planet's equator. Instead, Iapetus orbits Saturn from top to bottom.
. . Phoebe is 4 times more distant from Saturn than Iapetus, its nearest neighbor. Like Iapetus, it orbits Saturn nearly top to bottom.
July 13, 01: Astronomers have discovered 12 new Saturnine satellites, racking up its total to 30.
. . The 12 moons are unlike Luna in any way. They are all very small, with radii ranging from 3 km to 13 km, and all have large, eccentric orbits. They are likely from a bigger body that was broken up. The evidence for this resides in the common orbits the moons follow. Although one of the new moons does travel by itself, the other eleven occupy one of only four orbital routes.
. . "If somebody would do the same survey of Jupiter, they would be able to see down to one kilometer, while they could only see down to four kilometers at Saturn."
TITAN has an atmospheric density about four times that of Earth's. Balloons! Man-wings! I'd like to hear what % of its gravity is that of the atmosphere itself!
. . After nitrogen, methane is the most abundant component of Titan's atmosphere. Molecules of both substances are being continuously broken apart by ultraviolet solar photons, energetic electrons from Saturn's magnetosphere and cosmic rays.
. . Fragments of the parent molecules recombine and form more complex compounds. Photochemical models predict that ethane should be the main organic product of these atmospheric reactions.
. . If ethane and other complex organics rain down from the atmosphere onto Titan's surface, we would expect to find huge seas of ethane on Titan's surface. In fact, until recently it was believed that the surface of Titan was mainly composed of lakes or oceans of liquid hydrocarbons, with dry "islands" also covered with complex organic deposits.
Oct 22nd, 00: Clouds and even rain showers seem to have been spotted on Titan, Saturn's largest moon. Along with vast seas and modest mountains, a picture is emerging of a place more like Earth than anywhere else in the solar system. "Most rivers on Titan may run dry, but river valleys may nevertheless be abundant and deep." Most if not all of Titan's water is locked in ice.
. . Titan receives about 100 times less solar energy; temperatures hover around minus 288 degrees Fahrenheit (minus-178 degrees Celsius).
. . Titan's gravity is only about one-seventh that of Earth. The intense chill, however, means a low-energy atmosphere that hangs around, instead of escaping this relatively weak force of gravity. So Titan's atmosphere is denser than Earth's and extends much higher into the sky.
MIRANDA --466 km diameter-- is the Solar system's strangest moon. It has a sawtooth pattern of ridges, along with an unintelligible collection of light and dark rectangles... a large, bright streak shaped like a chevron, set within a patch of dark, tortured ground. This in turn was surrounded by a battered expanse of craters resembling the lunar highlands.
. . Along the edge of Miranda's sunlit face, a wide band of ridges and grooves cut across the surface like a racetrack and made a right-angle turn before disappearing into the darkness. Finally, there was a range of forbidding mountains, sliced by a towering cliff several km high.
. . Billions of years ago, Miranda may have been the victim of a cosmic collision, an impact so violent that it broke the moon into pieces --some icy, some rocky. Later on, said the theory, these fell back together into a hodge-podge of chunks. Relatively pure ice would show up as bright areas, while dark areas would consist of ice mixed with carbon-rich compounds darkened by exposure to high-energy cosmic radiation.
. . But the main theory about how it formed --after being blown to bits-- is being questioned by recent thinking.
. . No resonances exist between Miranda and the other Uranian satellites today. But theorists have calculated that resonances could have existed in the distant past, as Miranda's orbit changed. The result: A temporary heat-pulse that heated Miranda's interior just long enough to produce the observed features.
. . One face of Mimas was scarred by a crater so big that the impact must have come close to shattering the tiny moon. In all likelihood, Mimas had sustained even larger impacts during the solar system's early history. It might have been broken up and reassembled not just once, but several times.
Cordelia and Ophelia orbit Uranus on either side of the planet's main ring. As a result, astronomers call them "shepherd" moons, like the two near Saturn's rings.

NEPTUNE'S
  1. Naiad is the closest to Neptune. 29km
  2. Thalassa: 40
  3. Despina: 74
  4. Galatea: 79
  5. Larissa: 104 x 89
  6. Proteus is second largest: 218 x 208 x 201
  7. Triton is by far the largest --1,353.4-- but probably did not form around Neptune. It's lowly getting lower and lower. Eventually, it will crash into Neptune.
  8. Nereid --170km-- is the outermost of Neptune's moons, and the third largest. It was probably captured. 170km. Density: 1.000 times water!
Triton, Neptune's largest, is one-third as massive as Luna. Density 2.05 times water. Voyager photographed giant geysers that blasted dark plumes of gas and dust up to five miles high. It found that Triton's surface is mainly frozen nitrogen and methane on top of frozen water (-260 C) that's as hard as granite. It orbits Neptune in the opposite direction from all the other satellites.

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