Meteorites

An artist's impression of meteoroids (potential meteorites) about to enter the earth's atmosphere.
Most meteorites which land on our planet are believed to have originated within the Asteroid Belt.

A small rocky or metallic object in orbit around the Sun (or another star). A meteoroid which strikes the Earth (or other large body) is called a meteorite. As a meteoroid encounters the Earth's atmosphere frictional heating begins at an altitude of 100 to 120 km. What happens next depends on the speed, mass, and friability (tendency to break up) of the meteoroid. Micrometeoroids radiate heat so effectively that they survive unchanged to reach the surface as micrometeorites. Objects about the size of sugar grains burn up as meteors or "shooting stars". Friable meteoroids break up and are destroyed at altitudes of 80 to 90 km. Those which are tougher survive longer and produce fireballs as their surface is melted and eaten away at temperatures of several thousand degrees. If they avoid destruction high up, they enter the lower, denser part of the atmosphere where they are rapidly decelerated. Finally, at subsonic speeds the fireball is extinguished and the residue falls to the ground as a meteorite. The last melted material on the surface of the object solidifies to form a thin, usually black, rind known as a fusion crust.

Meteorites are among the rarest materials found on earth and are also the oldest things any human has ever touched. Chondrules—small, colorful, grain-like spheres about the size of a pin head—are found in the most common type of stone meteorite, and give that class its name: the chondrites. Chondrules are believed to have formed in the solar nebula disk, even before the planets which now inhabit our solar system. Our own planet was probably once made up of chondritic material, but geologic processes have obliterated all traces of the ancient chondrules. The only way we can study these 4.6 billion year old mementoes from the early days of the Solar System is by looking at meteorites. And so meteorites become valuable to scientists as they are nothing less than history, chemistry, and geology lessons from space.

Meteor Showers

There are a number of periodic meteor showers visible each year in the night sky: the Perseids in August, and the Leonids in November usually being the most interesting to observe. The annual meteor showers are the result of our planet passing through debris trails left by comets. The meteors we see during those annual displays are typically small pieces of ice which rapidly burn up in the atmosphere and never make it to the surface of our planet. 



Perseid meteors appear to stream from a point —
called the radiant — in the constellation Perseus.
The shower is best after midnight local time, when the radiant
rises in the northeast.

Perseids. The best known of all meteor showers, the Perseids never fail to put on a good show and — thanks to the shower's late-summer peak — are usually widely observed. The earliest record of this event comes from China in a.d. 36. Generally visible from July 17 to August 24, meteor speed (37 miles [60 km] per second), brightness, and a high proportion of trains (45 percent) distinguish the Perseids from other showers active at this time. It became the first meteor shower linked to a comet (109P/Swift-Tuttle) in 1865. Models of the Perseids predict a gradual decline in activity from a peak in 2004. 



Leonids meteors

Leonids. Leonid meteors generally arrive between November 14 and 21, with a peak hourly rate on November 17 of between 10 and 15 meteors per hour; about half of these meteors leave trains that can persist for several minutes. Because Earth runs into the orbiting particles almost directly head-on, Leonid meteors travel faster than those of any other shower — 45 miles (71 km) per second. The shower's most notable feature is its habit of producing periodic, dramatic meteor storms as Earth intercepts streams of dense material ejected at previous returns of Comet Tempel-Tuttle. Our planet passed through such streams annually from 1998 to 2003. Computer models show that Jupiter's tug on the dense Leonid streams causes them to miss Earth until at least 2098. Because the stream responsible for the predicted outbursts was ejected in 1933, only its smallest particles have been able to drift into a path that Earth will intersect. This means any outburst, if one occurs at all, will be rich in faint meteors.



Comets

Comet Hyakutake: Great Comet of 1996.

Among the most brilliant and most rare objects in the night sky. These soaring beacons with their beautiful tails come from the outer realms of the Solar System. A comet is a small world which scientists sometimes call a planetesimal. They are made out of dust and ice, kind of like a dirty snow ball.



Comet McNaught Comet McNaught

Where do they come from?
Comets come from two places: The Kuiper Belt and the Oort Cloud. 

Imagine a place far, far away at the very edge of the Solar System. A place where millions of comets can be seen swishing around in every direction. These icy comets are orbiting the Sun in two different places, both of which are very distant. One place is called the Oort cloud, and the other is called the Kuiper Belt. 

Why do Comets leave their home in the Oort Cloud or Kuiper Belt?
A comet will spend billions of years in the Kuiper Belt or Oort Cloud. Sometimes two comets will come very close to each other, or even crash into one another. When this happens the comets change directions. Sometimes their new path will bring them into the Inner Solar System.

This is when a comet begins to shine. Up until now the comet has been among millions of others exactly the same, but as they approach the warmer Inner Solar System they begin to melt leaving behind magnificent tails.

Unfortunately, comets don't live very long once they enter the warmer part of the Solar System. Just like a snowman melts in the summer, comets melt in the Inner Solar System. Although it is the most glorious part of their lives, traveling through the Inner Solar System eventually kills them. After several thousand years they melt down to a little bit of ice and dust, not nearly enough to leave a tail. Some even melt away completely.

Asteroids

Asteroids, chunks of rock and metal that orbit the Sun, sometimes collide with the Earth. This is one possible explanation for the extinction of dinosaurs.

Asteroid Fact Sheet

Asteroids are chunks of rock and metal that orbit the Sun. They can be different shapes and sizes.

There are three major types of asteroids: C-Carbonaceous (comprised of ancient carbon silicates), S-Silicates (made of rocky silicates and iron), and M-Types (rich in metals, mostly nickel and iron).

Asteroids can be as small as the size of a pebble. The largest known asteroid is Ceres, which is around 597 miles (960 kilometers) in diameter.

The largest population of asteroids lies between the orbits of Mars and Jupiter. However, a significant amount of asteroids are found within the orbits of Mars, Earth, Venus, and Mercury. Less than 200 asteroids orbit close enough to Earth to be considered a threat. These bodies are known as near-Earth objects.

Asteroid Belt  Most asteroids orbit the Sun between Mars and Jupiter. This area is called the Asteroid Belt. There are millions of asteroids. There are over 10,000 identified bodies in the asteroid belt that are between 60 miles (100 km) and 600 miles (1,000 km) across.  Very large asteroids, often called minor bodies, are large enough that their own gravity shapes them into spheres. Ceres and Vesta are two such examples. One possible explanation for the extinction of dinosaurs is that an asteroid hit Earth 65 million years ago. The theory holds that the impact brought catastrophic conditions, such as firestorms and light-blocking dust filling the atmosphere, that wiped out plant and animal life.

 

Moon



Moon just past full, in the darkness
of the night sky.

The Moon is Earth's only known natural satellite, and the fifth largest satellite in the Solar System. It is the largest natural satellite of a planet in the Solar System relative to the size of its primary, having a quarter the diameter of Earth and ¹⁄₈₁ its mass. The Moon is the second densest satellite after Io(moon), a satellite of Jupiter. It is in synchronous rotation with Earth, always showing the same face; the near side is marked with dark volcanic maria(lunar mare) among the bright ancient crustal highlands and prominent impact craters. It is the brightest object in the sky after the Sun, although its surface is actually very dark, with a similar reflectance to coal. Its prominence in the sky and its regular cycle of phases have since ancient times made the Moon an important cultural influence on language, calendars, art and mythology. The Moon's gravitational influence produces the ocean tides and the minute lengthening of the day. The Moon's current orbital distance, about thirty times the diameter of the Earth, causes it to appear almost the same size in the sky as the Sun, allowing it to cover the Sun nearly precisely in total solar eclipses.

The Moon, located 238,000 miles from Earth, has a temperature of 225° F during the day and drops down to –243° at night. With a diameter of 2,159 miles (3,475 kilometers), the Moon is just one-quarter the size of Earth. The Moon spins on its axis once every 27.3 Earth days. It takes the Moon 27.3 Earth days to revolve around our planet one time.

The Moon's surface is covered with craters, mountain ranges, rilles (long narrow channels), and lava plains. The vast, dark regions we see on the Moon's surface are called maria, or seas. They are actually very large, smooth lava beds. The bright, light areas on the Moon's surface are called highlands. The Moon is covered with a solid, rocky crust about 500 miles (800 km) thick. Underneath the crust, scientists think there is a partially molten zone that leads to a small core of iron. Craters on the Moon come in a wide variety of sizes. The largest crater measures 1,600 miles (2,575 km) across, while the smallest is the size of a pinprick.

To escape the Moon's gravity, you need to travel 5,200 miles (8,400 km) per hour, compared to 25,000 miles (40,200 km) per hour necessary to escape Earth's gravity. Earth's gravity is six times greater than the Moon's.

Apollo 11-17 First man on the Moon - Apollo Moon Landings

On July 20 ( July 21 GMT ) 1969 the first man stepped on the moon. During the next 3 years 6 missions to the moon was made and a total of 12 astronauts walked on the moon. These missions returned over 380 kg of lunar rocks, which have been used to develop a detailed geological understanding of the Moon's origins (it is thought to have formed some 4.5 billion years ago in a giant impact event involving Earth), the formation of its internal structure, and its subsequent history. After the Apollo 17 mission in 1972, the Moon has been visited only by unmanned spacecraft, notably by the final Soviet Lunokhod rover.

 

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The Phases of The Moon

The monthly changes of angle between the direction of illumination by the Sun
and viewing from Earth, and the phases of the Moon that result

Throughout each month the moon will change from a crescent shape to a full moon. The stages in between are called phases. After seven days the moon will change from a crescent to a half moon. For the next seven days the moon will change from being a half moon to a full moon. The reason why it has full and half moons depends on how the sunlight reflects off of the surface of the moon and how much of it we can see. The shadow on the moon always goes from east to west. The line that divides the part we can see from the dark part is called the terminator.

The moon rises and sets every day, appearing on the horizon just like the sun. The time depends on the phase of the moon. It rises about 30 to 70 minutes later each day than the previous day, so the moon is out during daytime as often is it's out at night. At the time of the new moon, the moon rises at about the same time the sun rises, and it sets at about the same time the sun sets. As the days go by (as it waxes to become a crescent moon, a half moon, and a gibbous moon, on the way to a full moon), the moon rises during daytime (after the sun rises), rising later each day, and it sets at nighttime, setting later and later each night. At the full moon, the times of moonrise and moonset have advanced so that the moon rises about the same time the sun sets, and the moon sets at about the same time the sun rises. As the moon wanes (becoming a half moon and a crescent moon, on the way to a new moon), the moon rises during the night, after sunset, rising later each night. It then sets in the daytime, after the sun rises. Eventually, the moon rises so late at night that it's actually rising around sunrise, and it's setting around sunset. That's when it's a new moon once again.

 

 

 

       Learn About The Planets

Solar System - SUN

The Sun is the most prominent feature in our solar system. It is the largest object and contains approximately 98% of the total solar system mass. One hundred and nine Earths would be required to fit across the Sun's disk, and its interior could hold over 1.3 million Earths. The Sun's outer visible layer is called the photosphere and has a temperature of 6,000°C (11,000°F). This layer has a mottled appearance due to the turbulent eruptions of energy at the surface.

Solar System - SUN

The Sun is a star - it is not a planet. Our Sun is just like the stars we see in the night sky. The Sun is also the only star we see during the daytime. The Sun is about 75% hydrogen and 25% helium. This changes slowly over time as the Sun converts hydrogen to helium in its core (center). Beside, the Sun's energy is produced by nuclear fusion reactions. It generates 386 billion megawatts of energy. The sun Contains darkspots that are known as sunspots.

Mercury

Mercury

Mercury - the closest planet to the Sun, takes only 88 days to orbit the Sun.

Size - Mercury is about 3,032 miles (4,880 kilometers) across. That makes it the smallest planet in the solar system. In fact, Mercury is just a little larger than Earth's Moon.

Distance from the Sun - Mercury is the closest planet to our star, with its average distance from the Sun being 36 million miles (58 million km).

Orbit around the Sun - Because Mercury is so close to the Sun, it has the smallest orbit of all the planets. Mercury's year (the time it takes to orbit the Sun one time) is 88 Earth days long.

Rotation - Although Mercury goes around the Sun quickly, it spins very slowly on its axis — about 59 Earth days for every rotation.

Surface - Scientists believe that Mercury has a thin, rocky crust, with a large metallic core, probably made of iron, at its center. Mercury is covered with craters and has ice at its poles.

Atmosphere - Mercury has an extremely thin atmosphere of helium and hydrogen captured from the solar wind.

Temperature - On Mercury, you would either freeze or roast. The highest surface temperature is 870° F (466° C), while the lowest temperature is –300 °F (–184 °C).

Escape velocity -  To escape Mercury's gravity, you have to travel 9,600 miles (15,500 km) per hour, compared to 25,000 miles (40,200 km) per hour necessary to escape Earth's gravity.

 

Venus
The surface of Venus, the brightest object in the sky after the Sun and Moon, is covered with craters, mountains, volcanos, and lava plains.

After the Sun and Moon, Venus is the brightest object in the sky. Because its thick clouds reflect most of the light Venus gets from the Sun, the planet looks like a very bright star in the morning (just before sunrise) or evening (just after sunset) sky.

Sometimes called Earth's sister planet, Venus is slightly smaller than Earth. It's also our closest neighbor, approaching within 25 million miles (40 million km).

Venus

In Roman mythology, Venus was identified with the goddess of love and beauty, Aphrodite. To the ancient Mayans, Venus was the patron planet of warfare called Kukulcan, or the feathered serpent.

Size - Venus is about 7,521 miles (12,104 kilometers) in diameter.

Distance from the Sun - The second planet from our star has an average distance from the Sun of 67 million miles (108 million km).

Orbit around the Sun - It takes 225 Earth days for Venus to go around the Sun one time.

Rotation - Venus spins on its axis once every 243 Earth days, but it spins in the opposite direction of Earth. On Venus, the Sun rises in the west and sets in the east.

Surface - The surface of Venus is covered with craters, mountains, volcanoes, and lava plains. Maxwell Montes is the highest point on Venus. It is more than 7 miles (11 km) high.

Atmosphere - Possessing sulfuric acid clouds, the atmosphere of Venus is mostly carbon dioxide (96 percent), nitrogen (3.5 percent), and carbon monoxide, argon, sulfur dioxide, and water vapor (all less than 1 percent). The atmosphere is so thick and heavy that it bends light, making the ground appear to curve upward in all directions. The planet's atmosphere is ninety times heavier than Earth's.

Temperature - Venus's surface temperature can get close to 900° F (482° C), hot enough to melt lead. This makes Venus the hottest place in the solar system after the Sun. Escape velocity -  To escape Venus's gravity, you have to travel 23,300 miles (37,500 km) per hour, compared to 25,000 miles (40,200 km) per hour necessary to escape Earth's gravity.

Earth

Earth is the third planet from the Sun and takes 23 hours, 56 minutes to spin on its axis one time.

Earth

Size - Earth has a diameter of 7,926 miles (12,756 kilometers).

Distance from the Sun - Earth is the third planet from the Sun, which is about 93 million miles (150 million km) away.

Orbit around the Sun - Earth goes around the Sun in 365 and 1/4 days. Every 4 years, the extra quarters add up to one whole day and we add a day to the end of February, creating a leap year.

Rotation - It takes only 23 hours, 56 minutes (1 day) for Earth to spin on its axis one time relative to the stars.

Surface - From space, Earth looks like the blue water world it is. About 70 percent of Earth's surface is covered with water, and 97 percent of all that water is in the salty oceans. Only 3 percent of Earth's water is freshwater — the water we drink. Earth is covered with mountains, volcanoes, lakes, rivers, and oceans. Most of the surface material is made of rocks — high in silica, iron, and magnesium.

Atmosphere - Earth's atmosphere is a mixture of gasses that becomes thinner as we move away from the planet toward space. Most of the atmosphere is nitrogen (78 percent), oxygen (21 percent), argon, and other gases (1 percent). Some of the oxygen in Earth's atmosphere has changed over time to form ozone. Earth's high ozone layer filters out the Sun's harmful ultraviolet rays, protecting the living beings on the surface. Ozone at ground level, however is an irritant to eyes, nose, and throats. Temperature - Earth's average temperature is 60° F (15.5° C). Escape velocity - To escape Earth's gravity, you have to travel 25,000 miles (40,200 km) per hour.

Mars 
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance.

Mars

Size - Mars is about 4,212 miles (6,779 kilometers) in diameter.

Distance from the Sun - Mars is the fourth planet from the Sun and orbits roughly 142 million miles (229 million km) away.

Orbit around the Sun - It takes 687 Earth days for the Red Planet to go around the Sun one time. Rotation - Mars spins on its axis at about the same speed as Earth does. It takes 24 hours and 37 minutes (about 1 Earth day) for Mars to rotate one time. Atmosphere - The martian atmosphere is very thin and made of carbon dioxide (95 percent), nitrogen (3 percent), argon and other gases (1 percent). Temperature - The lowest surface temperature on Mars is –190° F (–123° C), while the hottest temperature is 90° F (32° C).

Surface - There are lots of dry channels on Mars, and they look like Earth's river channels. Most scientists believe water once flowed on the martian surface, but new studies suggest there still may be water in some places at and under the surface. Mars has the largest canyon (Valles Marineris), and the highest volcano (Olympus Mons) in the solar system. If Valles Marineris were on Earth, it would span the United States, from New York on the East Coast to California on the West Coast. The canyon is about 1,300 miles (2,100 km) long, 300 miles (500 km) wide, and about 5 miles (8 km) deep. Olympus Mons is about three times higher than Mount Everest. It rises above the Martian surface 14 miles (22 km). This giant volcano's base is the size of the state of Missouri. The planet's reddish color is caused by rust (iron oxide) in the soil. The polar ice caps on Mars are made of frozen carbon dioxide, or dry ice, plus a seasonal coating of water ice.

Escape velocity - To escape the gravity of Mars, you have to travel 11,200 miles (18,000 km) per hour, compared to 25,000 miles (40,200 km) per hour necessary to escape Earth's gravity.

Jupiter 

Jupiter

Jupiter is the largest planet in our solar system, with a diameter of 89,000 miles. Jupiter has a "pizza moon." Sulfur-spewing volcanoes cover the surface of Io. At different temperatures, sulfur appears in different colors, making Io look like a giant pizza.

Size - Eleven Earths would fit side by side across the face of Jupiter. It is the biggest planet in the solar system, and it has a diameter of 89,000 miles (143,000 kilometers).

Distance from the Sun - Jupiter is the fifth planet from the Sun. Its orbit is about 483 million miles (777 million km) away from the Sun. That's five times farther than Earth's orbit.

Orbit around the Sun - It takes Jupiter 12 Earth years to go around the Sun once. So on your twelfth birthday, Jupiter is in roughly the same place of the solar system as it was on the day you were born.

Rotation - Although Jupiter takes a long time to go around the Sun, it takes only 10 hours to spin on its axis one time. That's less than half the time it takes Earth to spin once.

Surface - Jupiter does not have solid surface — its gaseous material becomes denser with depth.

Atmosphere - Jupiter's atmosphere is made mostly of hydrogen (86 percent) and helium (14 percent). The colorful cloud bands we see are actually cloud layers. Darker clouds tend to be deeper in Jupiter's atmosphere, while the lighter or white clouds are higher. The atmosphere also has giant lightning storms in its upper clouds.

Temperature - The average temperature at the top of Jupiter's clouds is –244° F (–153° C). Escape velocity - To escape Jupiter's gravity, you have to travel 133,100 miles (214,200 km) per hour, compared to 25,000 miles (40,200 km) per hour necessary to escape Earth's gravity.

Saturn

Saturn

Saturn, the sixth planet from the Sun, has a ring system made up of ice and rock particles, some as big as a minivan. Saturn is also called the "ringed planet." Although Jupiter, Uranus, and Neptune also have ring systems, Saturn's is the largest.

Size - Saturn would hold 9 1/2 Earths spread across its face. It is the second-largest planet in the solar system and has a diameter of 74,900 miles (120,500 kilometers).

Distance from the Sun - Saturn is the sixth planet from the Sun, with an orbit roughly 888 million miles (1.43 billion km) away.

Orbit around the Sun - Saturn journeys 29.4 Earth years to go around the Sun once.

Rotation - It takes Saturn only 11 hours to spin on its axis one time.

Surface - Saturn does not have solid surface.

Atmosphere - The atmosphere of this ringed planet is like Jupiter's atmosphere. Saturn holds mostly hydrogen (97 percent) and helium (3 percent). Saturn also has beautiful bands like Jupiter, but these colorful features are hidden by haze and smog that make up the planet's high atmosphere.

Temperature - The average temperature on Saturn is –300° F (–184° C). Escape velocity - To escape Saturn's gravity, you need to travel 79,400 miles (127,800 km) per hour, compared to 25,000 miles (40,200 km) per hour necessary to escape Earth's gravity.

 

Uranus

Uranus, the third-largest planet in the solar system, has an average temperature of –350° F and does not have a solid surface. Uranus is the planet tipped on its side. Uranus spins more like a barrel on its side than a top. This strange tilt may be the result of a collision with another body that tipped Uranus on its side.

In mythology, Uranus was the father of Saturn and grandfather of Jupiter.

Uranus Size - About 4 Earths would fit side by side across the face of Uranus. Its diameter is 31,800 miles (51,100 kilometers), making it the third-largest planet in the solar system.    Distance from the Sun - The seventh planet from the Sun, Uranus orbits at a distance of about 1.8 billion miles (2.9 billion km), more than 19 times farther than Earth's orbit. Orbit around the Sun - Uranus goes around the Sun once every 84 Earth years. Rotation - Uranus spins on its axis one time every 17 hours. Surface - Uranus does not have solid surface. Atmosphere - The atmosphere of Uranus holds hydrogen (83 percent), helium (15 percent), and methane (2 percent). Methane is what gives Uranus its blue-green color.

Temperature - Uranus is very cold — its average temperature is –350° F (–210° C). Escape velocity - To escape the gravity of Uranus, you need to travel 47,600 miles (76,600 km) per hour, compared to 25,000 miles (40,200 km) per hour necessary to escape Earth's gravity.

Neptune

Neptune has 13 moons, the two largest are Triton and Nereid. Triton is made of rock and ice. Its surface is rich in water ice, dry ice, frozen carbon monoxide, methane, and nitrogen. Triton has cold geysers that spit nitrogen instead of the hot water that geysers on Earth release. Neptune was only the god of water, but later on this was extended to include the sea when he became associated with the Greek god Poseidon.

Neptune

Size - Neptune is slightly smaller than Uranus and has a diameter of 31,000 miles (50,000 kilometers), so about 4 Earths would fit across its face. Distance from the Sun - Neptune is the eighth planet from the Sun. It orbits at an average distance of 2.8 billion miles (4.5 billion km), thirty times farther than Earth. Orbit around the Sun - It takes 165 Earth years for Neptune to go around the Sun one time. Rotation - It takes Neptune only 16 Earth hours for it to spin on its axis once.  Surface - Like the other gas-giant planets, Neptune's "surface" is the top of its deep atmosphere. This contains hydrogen (79 percent), helium (18 percent), and methane (3 percent), which gives the planet its blue color. Neptune's atmosphere has a striped pattern like both Jupiter's and Saturn's.

Temperature - The average temperature at Neptune is –370° F (–220° C). Escape velocity - To escape Neptune's gravity, you need to travel 52,600 miles (84,700 km) per hour, compared to 25,000 miles (40,200 km) per hour necessary to escape Earth's gravity.

Pluto

Pluto

Pluto, reclassified as a dwarf planet in 2006, is located nearly 40 times as far from the Sun as Earth.

In July 1978, James Christy discovered Pluto's moon, Charon. This moon is about half as big as Pluto itself. In May 2005, astronomers used the Hubble Space Telescope to hunt for undiscovered moons around Pluto. They found two moons,provisionally known as S/2005 P1 and S/2005 P2.

Pluto was thought to be the god to whom all men must eventually go. Romans believed him to be the god of the underworld. In Greek mythology, he is known as Hades.

Size - With a diameter of only 1,485 miles (2,390 kilometers), Pluto was the smallest planet in the solar system. In 2006, the International Astornomical Union reclassified Pluto as a dwarf planet. Distance from the Sun - Pluto was the ninth planet from the Sun. It orbits our star at a distance of 3.6 billion miles (5.9 billion km), nearly forty times as far from the Sun as Earth. Orbit around the Sun - It takes Pluto 248 Earth years to go around the Sun one time. Rotation - Pluto spins on its axis once every 6 Earth days. Surface - Pluto's surface has dark markings and probably is made of methane and nitrogen ice on top of a rock and water ice mixture. Atmosphere - Pluto has a very thin atmosphere of nitrogen and methane.

Temperature - The average temperature on Pluto is –390° F (–235° C). Escape velocity - To escape Pluto's gravity, you need to travel 2,500 miles (4,000 km) per hour, compared to 25,000 miles (40,200 km) per hour necessary to escape Earth's gravity.