Mrs. Babcock's You Gotta Know these Moons and Planets

The Moon's The flat dark lunar plains

Maria (singular: mare) and are mainly concentrated on the near side of the moon. The most famous one is Mare Tranquillitatis, the Sea of Tranquility, where Apollo 11 first landed on the moon in 1969. The Apollo program landed on the moon five more times.

Saturn

The sixth planet from the sun, Saturn is known most for its rings. When polymath Galileo Galilei first studied Saturn in the early 1600s, he thought it was an object with three parts: a planet and two large moons on either side. Not knowing he was seeing a planet with rings, the stumped astronomer entered a small drawing — a symbol with one large circle and two smaller ones — in his notebook, as a noun in a sentence describing his discovery. More than 40 years later, Christiaan Huygens proposed that they were rings. The rings are made of ice and rock and scientists are not yet sure how they formed. The gaseous planet is mostly hydrogen and helium and has numerous moons. Discovery: Known to the ancient Greeks and visible to the naked eye Named for Roman god of agriculture Diameter: 74,900 miles (120,500 km) Orbit: 29.5 Earth years Day: About 10.5 Earth hours

Venus

The second planet from the sun, Venus is Earth's twin in size. Radar images beneath its atmosphere reveal that its surface has various mountains and volcanoes. But beyond that, the two planets couldn't be more different. Because of its thick, toxic atmosphere that's made of sulfuric acid clouds, Venus is an extreme example of the greenhouse effect. It's scorching-hot, even hotter than Mercury. The average temperature on Venus' surface is 900 F (465 C). At 92 bar, the pressure at the surface would crush and kill you. And oddly, Venus spins slowly from east to west, the opposite direction of most of the other planets. The Greeks believed Venus was two different objects — one in the morning sky and another in the evening. Because it is often brighter than any other object in the sky, Venus has generated many UFO reports. Discovery: Known to the ancient Greeks and visible to the naked eye Named for the Roman goddess of love and beauty Diameter: 7,521 miles (12,104 km) Orbit: 225 Earth days Day: 241 Earth days

Phobos

Both Phobos ("fear") and Mars' smaller moon Deimos ("dread") were discovered by Asaph Hall III in 1877. At just 3,700 miles above the Martian surface, Phobos orbits more closely to its planet than any other moon in the Solar System. Because it orbits Mars faster than Mars rotates, each day it appears (from the Martian surface) to set twice in the east. Geological features on Phobos, including the Stickney Crater, are primarily named for either astronomers (Stickney was the maiden name of Asaph Hall's wife) or characters from Jonathan Swift's Gulliver's Travels. In 1971 the U.S.'s Mariner IX became the first spacecraft to provide close-up photos of Phobos.

Mars

Fourth planet from the sun is Mars, and it's a cold, desert-like place covered in dust. This dust is made of iron oxides, giving the planet its iconic red hue. Mars shares similarities with Earth: It is rocky, has mountains, valleys and canyons, and storm systems ranging from localized tornado-like dust devils to planet-engulfing dust storms. Substantial scientific evidence suggests that Mars at one point billions of years ago was a much warmer, wetter world. Rivers and maybe even oceans existed. Although Mars' atmosphere is too thin for liquid water to exist on the surface for any length of time, remnants of that wetter Mars still exist today. Sheets of water ice the size of California lie beneath Mars' surface, and at both poles are ice caps made in part of frozen water. In July 2018, scientists revealed that they had found evidence of a liquid lake beneath the surface of the southern pole's ice cap. It's the first example of a persistent body of water on the Red Planet. Scientists also think ancient Mars would have had the conditions to support life like bacteria and other microbes. Hope that signs of this past life — and the possibility of even current lifeforms — may exist on the Red Planet has driven numerous space exploration missions and Mars is now one of the most explored planets in the solar system. Discovery: Known to the ancient Greeks and visible to the naked eye Named for the Roman god of war Diameter: 4,217 miles (6,787 km) Orbit: 687 Earth days Day: Just more than one Earth day (24 hours, 37 minutes)

Mercury

Innermost world of our solar system. (Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington) Zipping around the sun in only 88 days, Mercury is the closest planet to the sun, and it's also the smallest, only a little bit larger than Earth's moon. Because its so close to the sun (about two-fifths the distance between Earth and the sun), Mercury experiences dramatic changes in its day and night temperatures: Day temperatures can reach a scorching 840 F (450 C), which is hot enough to melt lead. Meanwhile on the night side, temperatures drop to minus 290 F (minus 180 C). Mercury has a very thin atmosphere of oxygen, sodium, hydrogen, helium and potassium and can't break-up incoming meteors, so its surface is pockmarked with craters, just like the moon. Over its four-year mission, NASA's MESSENGER spacecraft revealed incredible new discoveries that challenged astronomers' expectations. Among those findings was the discovery of water ice and frozen organic compounds at Mercury's north pole and that volcanism played a major role in shaping the planet's surface. Discovery: Known to the ancient Greeks and visible to the naked eye Named for the messenger of the Roman gods Diameter: 3,031 miles (4,878 km) Orbit: 88 Earth days Day: 58.6 Earth days

Pluto (dwarf planet)

Once the ninth planet from the sun, Pluto is unlike other planets in many respects. It is smaller than Earth's moon; its orbit is highly elliptical, falling inside Neptune's orbit at some points and far beyond it at others; and Pluto's orbit doesn't fall on the same plane as all the other planets — instead, it orbits 17.1 degrees above or below. From 1979 until early 1999, Pluto had actually been the eighth planet from the sun. Then, on Feb. 11, 1999, it crossed Neptune's path and once again became the solar system's most distant planet — until it was redefined as a dwarf planet. It's a cold, rocky world with a tenuous atmosphere. Scientists thought it might be nothing more than a hunk of rock on the outskirts of the solar system. But when NASA's New Horizons mission performed history's first flyby of the Pluto system on July 14, 2015, it transformed scientists' view of Pluto. Pluto is a very active ice world that's covered in glaciers, mountains of ice water, icy dunes and possibly even cryovolcanoes that erupt icy lava made of water, methane or ammonia. Related: New Horizons' Pluto Flyby: Latest News, Images and Video Discovery: 1930 by Clyde Tombaugh Named for the Roman god of the underworld, Hades Diameter: 1,430 miles (2,301 km) Orbit: 248 Earth years Day: 6.4 Earth day

Deimos

One-seventh the mass of Phobos and further away from the Martian surface, Deimos was found by Asaph Hall at the U.S. Naval Observatory six days before he discovered Phobos. Its largest and only named craters are Swift and Voltaire; Deimos's surface doesn't appear as rough as Phobos's because regolith has filled in some of the craters. A still-controversial and unproven hypothesis holds that Deimos (and possibly Phobos as well) were asteroids perturbed out of their orbit by Jupiter and then captured by the gravity of Mars.

Planet Nine

Orbits of distant Kuiper Belt objects and the hypothesized Planet Nine. Orbits rendered in purple are primarily controlled by Planet Nine's gravity and exhibit tight orbital clustering. Green orbits are strongly coupled to Neptune and exhibit a broader orbital dispersion. Updated orbital calculations suggest that Planet Nine is an approximately 5-Earth-mass planet that resides on a mildly eccentric orbit with a period of about 10,000 years. The orbits of distant Kuiper Belt objects and the hypothesized Planet Nine around the sun are shown in this image.. Orbits in purple are primarily controlled by Planet Nine's gravity and exhibit tight orbital clustering. Green orbits are strongly coupled to Neptune and exhibit a broader orbital dispersion. Planet Nine is an approximately 5-Earth-mass planet that resides on a mildly eccentric orbit with a period of about 10,000 years. (Image credit: James Tuttle Keane/Caltech) In 2016, researchers proposed the possible existence of a ninth planet, for now dubbed "Planet Nine" or Planet X. The planet is estimated to be about 10 times the mass of Earth and to orbit the sun between 300 and 1,000 times farther than the orbit of the Earth. Scientists have not actually seen Planet Nine. They inferred its existence by its gravitational effects on other objects in the Kuiper Belt, a region at the fringe of the solar system that is home to icy rocks left over from the birth of the solar system. Also called trans-Neptunian objects, these Kuiper Belt objects have highly elliptical or oval orbits that align in the same direction. Scientists Mike Brown and Konstantin Batygin at the California Institute of Technology in Pasadena described the evidence for Planet Nine in a study published in the Astronomical Journal. The research is based on mathematical models and computer simulations using observations of six other smaller Kuiper Belt Objects with orbits that aligned in a similar matter. A recent hypothesis proposed September 2019 on the pre-print server arXiv suggests Planet Nine might not be a planet at all. Instead, Jaku Scholtz of Durham University and James Unwin of the University of Illinois at Chicago speculate it could be a primordial black hole that formed soon after the Big Bang and that our solar system later captured, according to Newsweek. Unlike black holes that form from the collapse of giant stars, primordial black holes are thought to have formed from gravitational perturbations less than a second after the Big Bang, and this one would be so small (5 centimeters in diameter) that it would be challenging to detect.

Iapetus

Saturn's third-largest moon after Titan and Rhea and, like Rhea, was discovered by Giovanni Cassini in 1671. It was named based upon a suggestion from John Herschel (son of the discoverer of Uranus, William Herschel) for the Titans of Greek mythology, the brothers and sisters of Cronos (Saturn). Iapetus has a distinctive two-tone coloration; part of it is red-brown, while part is bright gray. Features on Iapetus are named for people and places from the French Song of Roland, including Charlemagne Crater and the bright northern region Roncevaux Terra. In 2004 the Cassini orbiter found an equatorial ridge running over 800 miles long and 10 miles wide that gives Iapetus some of the highest peaks in the solar system; its existence has not yet been explained.

Neptune

The eighth planet from the sun, Neptune is about the size of Uranus and is known for supersonic strong winds. Neptune is far out and cold. The planet is more than 30 times as far from the sun as Earth. Neptune was the first planet predicted to exist by using math, before it was visually detected. Irregularities in the orbit of Uranus led French astronomer Alexis Bouvard to suggest some other planet might be exerting a gravitational tug. German astronomer Johann Galle used calculations to help find Neptune in a telescope. Neptune is about 17 times as massive as Earth and has a rocky core. Discovery: 1846 Named for the Roman god of water Diameter: 30,775 miles (49,530 km) Orbit: 165 Earth years Day: 19 Earth hours

Jupiter

The fifth planet from the sun, Jupiter is a giant gas world that is the most massive planet in our solar system — more than twice as massive as all the other planets combined, according to NASA. Its swirling clouds are colorful due to different types of trace gases. And a major feature in its swirling clouds is the Great Red Spot, a giant storm more than 10,000 miles wide. It has raged at more than 400 mph for the last 150 years, at least. Jupiter has a strong magnetic field, and with 75 moons, it looks a bit like a miniature solar system. Discovery: Known to the ancient Greeks and visible to the naked eye Named for the ruler of the Roman gods Diameter: 86,881 miles (139,822 km) Orbit: 11.9 Earth years Day: 9.8 Earth hours

Io

The innermost of the four Galilean moons of Jupiter (the moons discovered by Galileo), the fourth-largest moon in the solar system, the densest moon, and the most geologically active body in the solar system, with more than 400 volcanoes. Io's features are named for characters from the Io story in Greek mythology; fire, volcano, and thunder deities from other mythologies; and characters from Dante's Inferno. Io plays a significant role in shaping Jupiter's magnetosphere. Pioneer 10 first passed by Io in December 1973.

Ganymede

The largest moon in the solar system and the only one known to have its own magnetosphere. The third of the Galilean satellites, Ganymede was also first photographed close-up by Pioneer 10 in 1973. Galileo made six flybys of Ganymede between 1996 and 2000. Based on a suggestion from Simon Marius, Ganymede (along with many of the Jovian satellites) is named for one of Jupiter's lovers in Roman mythology; Ganymede is the only such moon named for a male figure. Many of Ganymede's features, including the Enki Catena, are given names from Egyptian and Babylonian mythology, although its largest dark plain is Galileo Regio. Ganymede is scheduled to be orbited by the European Space Agency's Jupiter Icy Moon Explorer (JUICE), currently slated for a 2022 launch.

Triton

The largest moon of Neptune and the only large moon with a retrograde orbit (that is, an orbit opposite to the rotation of its planet), Triton is the seventh-largest moon in the solar system and is thought to have been captured from the Kuiper Belt. For over 100 years after its 1846 discovery, Triton was thought to be Neptune's only moon; Nereid wasn't discovered until 1949. (There are thirteen known satellites now.) Triton is geologically active and has geysers that are assumed to erupt nitrogen. Because of the activity, impact craters on Triton are relatively scarce; most of the larger craters were formed by volcanic activity. Triton orbits around Neptune in almost a perfect circle. Voyager 2 visited Triton in 1989 and is the only space probe to have done so (and no more are currently planned). Much of Triton's western hemisphere consists of an unexplained series of fissures and depressions sometimes called "cantaloupe terrain." Triton's features are named after various water spirits, monsters, and sacred waters from mythology.

Titan

The largest moon of Saturn and the second-largest in the solar system. Until Voyager 1 visited in 1980, it was thought to be larger than Ganymede. It is the only known satellite with a dense atmosphere — so dense that it makes observation of surface features nearly impossible except from close up — and also the only known satellite for which there is evidence of stable bodies of surface liquid. Discovered in 1655 by Christiaan Huygens, it was visited by the Cassini-Huygens mission in 2004. Titan's albedo features, such as the highly reflective area Xanadu, are named for sacred or enchanted places from world literature and mythology. Because of its nitrogen-rich atmosphere and the presence of surface liquid, Titan is often thought to be the most likely place in the solar system for microbial life to exist outside of Earth.

Charon

The largest satellite of the dwarf planet Pluto, Charon wasn't discovered until 1978. (As of 2013, Pluto has five known moons, the last two discovered in 2011 and 2012.) Unlike Pluto, which is covered with nitrogen and methane ices, Charon appears to be covered in water ice and may also have active cryo-geysers. Because the center of mass of the Pluto-Charon system lies outside of either one, Charon doesn't truly orbit Pluto; when Pluto was reclassified as a dwarf planet in 2006, an argument was made (but not accepted) to classify Pluto-Charon as a binary system. The IAU still considers Charon, which is roughly half the size but has only 11% the mass of Pluto, to be a satellite. The New Horizons mission visited Charon and Pluto in 2015. Charon was named by its discoverer, James Christy of the Flagstaff Naval Observatory; the IAU approved the name in 1985. Internationally Charon is pronounced like the Greek mythological figure, "CARE-on", but Christy's choice of name was inspired by his wife Charlene, so NASA and New Horizons personnel use "SHARE-on".

Earth's Moon

The moon, also called Luna, is the fifth-largest satellite in the solar system, the largest relative to the size of the planet it orbits, and the second densest. The USSR's Luna unmanned spacecraft first reached the moon in 1959, and Apollo 8 became the first manned mission to orbit the moon, in 1968. The 1967 Outer Space Treaty guarantees the rights of all nations to explore the moon for peaceful purposes.

Uranus

The seventh planet from the sun, Uranus is an oddball. It has clouds made of hydrogen sulfide, the same chemical that makes rotten eggs smell so foul. It rotates from east to west like Venus. But unlike Venus or any other planet, its equator is nearly at right angles to its orbit — it basically orbits on its side. Astronomers believe an object twice the size of Earth collided with Uranus roughly 4 billion years ago, causing Uranus to tilt. That tilt causes extreme seasons that last 20-plus years, and the sun beats down on one pole or the other for 84 Earth-years at a time. The collision is also thought to have knocked rock and ice into Uranus' orbit. These later became some of the planet's 27 moons. Methane in the atmosphere gives Uranus its blue-green tint. It also has 13 sets of faint rings. Discovery: 1781 by William Herschel (was originally thought to be a star) Named for the personification of heaven in ancient myth Diameter: 31,763 miles (51,120 km) Orbit: 84 Earth years Day: 18 Earth hours

Earth

The third planet from the sun, Earth is a waterworld, with two-thirds of the planet covered by ocean. It's the only world known to harbor life. Earth's atmosphere is rich in nitrogen and oxygen. Earth's surface rotates about its axis at 1,532 feet per second (467 meters per second) — slightly more than 1,000 mph (1,600 kph) — at the equator. The planet zips around the sun at more than 18 miles per second (29 km per second). Name originates from "Die Erde," the German word for "the ground." Diameter: 7,926 miles (12,760 km) Orbit: 365.24 days Day: 23 hours, 56 minutes

Titania and Oberon

Uranus's largest moons, Titania and Oberon, are named for characters from Shakespeare's A Midsummer Night's Dream. (Other Uranian moons are named for characters from either Shakespeare or Alexander Pope.) They were discovered on the same day in 1787 by William Herschel, who also discovered Uranus itself in 1781. In 1986 Voyager 2 became the only spacecraft to date to visit the Uranian moons. Because Uranus orbits the sun almost on its side and Titania and Oberon orbit Uranus in the same plane as its equator, the moons have extreme seasons: Titania's poles spend over 42 years in nonstop sunlight followed by 42 years of darkness. Most of Titania's features are named for settings or female characters from Shakespeare — its largest crater is Gertrude Crater, after Hamlet's mother — while most of Oberon's are named after settings or male characters from Shakespeare. However, Oberon's largest feature is Mommur Chasma, which is named from a French epic poem.