EARTH:
Almost all of the Oxygen in the Earth's atmosphere has been produced
by living organisms. Oxygen accounts for 21% of our atmosphere,
with Nitrogen making up 78%, and a mixture of other gases composing
the remaining 1%. Oxygen only occurs as a minor constituent in
the atmospheres of other planets in our Solar System.
(11/27/95)
The Earth has the highest average density (5.52 g/cubic cm) of
any planet in our Solar System. Saturn has the lowest (0.69 g/cubic
cm). For reference, the density of liquid water is 1 g/cubic cm.
(8/23/96)
During a lunar eclipse, one can view the curved shape of the Earth's
shadow, which is naked eye, groundbased evidence that the Earth
is indeed round.
(9/20/96)
JUPITER:
Did you know that the most volcanically active body in the solar
system besides the Earth is Jupiter's moon Io. Erupting volcanoes
were discovered on Io by the Voyager spacecraft.
(9/18/95)
Jupiter's magnetosphere is the largest single structure inside
the Solar System. If you could see it with your eyes, it would
appear larger than our full Moon.
(12/27/95)
Jupiter's moon Europa may have a liquid water "ocean"
far beneath its water ice covered surface.
(1/3/96)
The Great Red Spot on Jupiter is a hurricane-like storm system.
It is large enough that two Earths could fit across it. The Red
Spot has been around since at least the early 1600's when it was
first detected shortly after the invention of the telescope.
(2/21/96)
From the Jupiter-facing side of the moon Amalthea, Jupiter would
fill up a huge chunk of sky: equivalent to going from the horizon
to half way above the horizon.
(4/24/96)
Jupiter's moon Io, less than 1/3 the size of Earth, puts out twice
as much heat as the Earth. This is primarily due to tidal forces
from Jupiter's enormous gravitational field causing a constant
squeezing and stretching of Io. Heat generated by that squeezing
and stretching accounts for Io being the most volcanically active
body in the Solar System.
(5/31/96)
Jupiter's moon Ganymede is the largest moon in the Solar System,
and is larger than the planets Mercury and Pluto.
(7/12/96)
A Jupiter day, the time required for the planet to rotate once,
is only about 10 hours long. Jupiter has the shortest day (rotation
period) of any planet in the Solar System.
(10/18/96)
Europa, covered with mostly water ice, has the smoothest surface
of any large object in the solar system. This satellite of Jupiter
has a mostly flat surface, with no discovered topographic relief
larger than 1 km (0.6 mi) in height, even though Europa has an
intricate set of cracks criss-crossing its icy surface.
(11/8/96)
Jupiter's moon Ganymede, the largest moon in the Solar System,
has a surface area that is approximately half that of Earth's
land surface area (not including Earth's oceans).
(12/30/96)
Jupiter's core is thought to consist primarily of metallic hydrogen.
(9/15/97)
MARS:
Did you know that liquid water does not currently occur on Mars
because of the cold temperatures and low atmospheric pressures.
Only water ice and water gas (vapor) are stable. However, large
channels on Mars appear to have been cut by outflows of liquid
water during Mars' distant past which may have had warmer temperatures
and a much thicker atmosphere.
(8/25/95)
The largest canyon system in the Solar System is Valles Marineris
on Mars. It is more than 3000 miles long and so would stretch
from California to New York. In some places it reaches 3 miles
in depth and 200 miles in width.
(11/6/95)
Mars' surface area is approximately the same as the surface area
of all the land (as opposed to water) on Earth. So, even though
Mars is a smaller planet, studying its surface is just as large
a task as studying all of Earth's land surfaces.
(11/1/96)
Mars has two large-scale geologic regions (in addition to many
smaller geologic variations within both regions). The "Southern
Highlands," which cover a little more than half of Mars'
surface, are composed of old (at least 3.9 billion years) densely
cratered terrain. The "Northern Plains" have lower and
more variable crater densities, indicating that the plains are
younger and formed over a much longer period of time. The cause
of this Martian geologic dichotomy is not yet agreed upon.
(12/9/96)
The gravitational force at the surface of Mars is only about one-third
as strong as the gravitational force at the surface of the Earth.
(2/12/97)
Many of the larger rocks at the Viking Lander sites on Mars were
given names. These included Toad, Badger, and Guppy, all of which
were named because of some resemblance to those creatures, as
well as ones named for all seven dwarfs, and the largest of the
rocks near the landers was named Big Joe.
(5/7/97)
At its closest approach to Earth, Mars appears about as big as
a tennis ball viewed from a distance of one and a half miles (two
and a quarter kilometers).
(11/20/97)
The main constituent of the Martian atmosphere, carbon dioxide,
actually freezes n the surface during the winter, particularly
in the polar regions. This can cause global atmoshperic pressure
changes. On Earth, water freezes out, but is a minor constituent
in the atmosphere.
(8/4/97)
MERCURY:
Did you know that water ice may exist in the bottoms of craters
at Mercury's poles, based upon radar data taken in recent years.
Even though Mercury is the closest planet to the Sun, and extremely
hot over most of its surface, ice may exist at the bottoms of
some polar craters because the crater floors are permanently shadowed
by the crater rims.
(10/16/95)
MOONS:
Did you know that some of the moons in our Solar System are larger
than some of the planets? Jupiter's moon Ganymede, the largest
moon in the Solar System, and Saturn's moon Titan are both larger
than the planets Mercury and Pluto. The Earth's Moon, Jupiter's
moons Callisto, Io, and Europa, and Neptune's moon Triton are
all larger than Pluto, but smaller than Mercury.
(1/17/96)
If you added up the mass of all of the thousands of known asteroids
in the asteroid belt, the total would be less than ten percent
the mass of the Earth's moon.
(3/20/96)
Our moon has only one eightieth the mass of the Earth.
(3/20/96)
A Blue Moon is the second of two full Moons that fall in the same
month. This can occur because full Moon's occur roughly every
29.5 days. A Blue Moon occurs roughly every two and three-quarter
years. So, now you know how long once in a Blue Moon really is.
(06/28/96)
The Earth's Moon has only about 1/80th the mass of Earth.
(7/3/96)
The Moon actually appears much brighter than the Sun at gamma
ray wavelengths (as seen from the Earth-orbiting Compton Gamma
Ray Observatory).
(1/29/97)
PLUTO:
Pluto's elliptical orbit sometimes brings it inside of the orbit
of Neptune for a few years. We are currently in one of those periods,
so right now Neptune is the farthest planet from the Sun.
(10/30/95)
On average, the distance from Pluto to the Sun is approximately
40 times the distance from the Earth to the Sun. Put a different
way, if a scale model were constructed with the Sun on the California
coast and the Earth about 75 miles inland, then on the same scale
Pluto would be in New York.
(3/6/96)
SATURN:
All four giant planets (Jupiter, Saturn, Uranus, and Neptune)
have ring systems. As of 20 years ago, only Saturn was known to
have rings. Saturn's ring system is by far the largest and most
developed of the four.
(6/7/96)
URANUS:
Methane gas, which absorbs red light, is what causes Uranus and
Neptune to look bluish in color. Methane is a relatively minor
constituent of their atmospheres, however. Like Jupiter and Saturn,
Uranus and Neptune have atmospheres made mostly of hydrogen and
helium.
(7/26/96)
The planet Uranus was discovered by the eminent English astronomer
William Herschel in 1781. He briefly considered naming the planet
George in honor of England's King George III.
(1/15/98)
VENUS:
The surface of Venus is obscured by clouds at ultraviolet, visible,
and infrared wavelengths, which is why the Pioneer and Magellan
spacecraft used radar to penetrate the clouds and image the surface.
(1/24/96)
The atmospheric pressure you would experience on the surface of
Venus is approximately equal to the pressure you would experience
3000 feet (approx. 1 km) down in the Earth's oceans, i.e., about
90 times the pressure at the Earth's surface.
(3/27/96)
Venus rotates very slowly. A Venus day, the time it takes Venus
to rotate once, is approximately 243 Earth days long.
(8/2/96)
Venus is the brightest natural object in the sky besides the Sun
and Moon. It can be as much as 15 times brighter than the brightest
star (Sirius).
(1/13/97)
All of the major features on the planet Venus are named after
famous women in history and mythology.
(10/22/97)
COMETS:
As comets approach the Sun, their tails can become long enough
that they stretch from one planet's orbit across the orbit of
another planet.
(10/11/96)
Comet Hale-Bopp is putting out approximately 250 tons of gas and
dust per second. This is about 50 times more than most comets
produce.
(4/8/97)
For the first 100 million years or so after the formation of the
solar system, a bright, naked-eye comet was visible in the skies
of Earth roughly once a week.
(2/15/98)
Based upon data from the International Ultraviolet Explorer (IUE)
satellite, Comet Hyakutake was found to be ejecting ten tons of
water every second as it passed near the Sun.
(10/4/96)
SPACE SHUTTLE:
It only takes the Space Shuttle about 8 minutes to accelerate
to its orbital speed of more than 17,000 miles per hour.
(9/1/95)
The Space Shuttle main engine weighs 1/7th as much as a train
engine, but delivers as much horsepower as 39 train engines.
(9/25/95)
Pioneer 11's speed going past Jupiter was over 107,000 mph, the
fastest speed ever traveled by a human-made object.
(10/2/95)
At almost six billion miles away, Pioneer 10 is the most distant
object built by humans.
(10/9/95)
A Space Shuttle and its boosters ready for launch are the same
height as the Statue of Liberty but weigh almost three times as
much.
(10/23/95)
Each of the Space Shuttle's solid rocket boosters burns 5 tons
of propellant per second.
(11/13/95)
The Galileo probe, weighing in at 339 kilograms (750 pounds),
will enter Jupiter's atmosphere at 170,000 kilometers per hour
(106,000 mph), or more than 50 times faster than a bullet shot
out of a rifle. The probe will experience deceleration forces
as high as 230 times Earth's gravity. In about two minutes, the
orbiter's speed will be slowed to about 1,600 kilometers per hour
(1,000 mph).
(12/4/95)
The amount of power transmitted by the Galileo spacecraft's radio
is about the same amount used by a refrigerator light bulb--about
20 watts. By the time they reach Earth, the radio signals from
Galileo are incredibly weak (about a billion times fainter than
the sound of a transistor radio in New York as heard from Los
Angeles).
(12/11/95)
The average radiation dose per minute absorbed by the Galileo
spacecraft during its orbital mission is equivalent to what the
average person receives in a whole year on Earth. On December
7, as it made its closest approach to Jupiter, the radiation dose
per minute to Galileo exceeded by several times what a person
on Earth would receive in their entire lifetime and would have
been quite lethal to a human.
(12/18/95)
The Voyager spacecraft delivery accuracy at Neptune (100 km or
60 mi.) (62 mi), divided by the trip distance of 7,128,603,456
km (4,429,508,700 mi), was the equivalent of sinking a 3630 km
(2260 mi.) golf shot, although Voyager, as opposed to a golf shot,
was allowed a few minor trajectory adjustments along the way.
(2/28/96)
It takes radio signals from Earth (traveling at the speed of light:
186,000 miles per second) approximately 9 hours to reach the Pioneer
10 spacecraft, which is the most distant object built by humans.
It takes another 9 hours for the spacecraft's response to reach
Earth.
(3/13/96)
NASA's Compton Gamma Ray Observatory, launched in 1991 aboard
the Space Shuttle Atlantis, is the heaviest spacecraft ever deployed
by a Space Shuttle.
(4/10/96)
The Space Shuttle flies about 200 miles (330 km) above the Earth's
surface (equivalent to roughly half the distance between Los Angeles
and San Francisco). In contrast, geostationary (stationary with
respect to the Earth's surface) communications satellites have
to be lofted approximately 21,500 miles (35,800 km) above the
Earth's surface, and the Apollo spacecraft were approximately
227,000 miles (378,000 km) above the Earth's surface when they
reached the Moon.
(4/17/96)
In its six years of operation, the Hubble Space Telescope has
observed approximately 8000 objects, which is roughly equivalent
to the number of stars that can be seen from the surface of Earth
with the naked eye.
(5/24/96)
It currently takes radio signals approximately 35 minutes to get
from the Galileo spacecraft to Earth. Galileo, in orbit around
Jupiter, is over 635 million kilometers (about 395 million miles)
from Earth.
(7/19/96)
The amount of power being transmitted by the Galileo spacecraft
radio is about the same as that used to power a refrigerator light
bulb--about 20 watts
(8/30/96)
The Solid Rocket Boosters (SRBs) used during Space Shuttle launches
are the largest solid-propellant motors ever flown and the first
designed for reuse. Each is 149.16 feet long and 12.17 feet in
diameter.
(9/13/96)
The speed required for a spacecraft or other object to completely
escape the gravitational pull of the Earth (escape velocity) is
approximately 11 km/s (7 mi/s), or about 40,000 km/hr (25,000
mi/hr).
(9/27/96)
The Galileo spacecraft traveled 2.4 billion miles on its way to
Jupiter and along the way used about 67 gallons of fuel to control
the flight path and spacecraft attitude. This is the equivalent
of about 36 million miles per gallon, although Galileo's usage
of fuel was not at all continuous, but rather occurred in discrete
bursts.
(10/25/96)
Each Space Shuttle Solid Rocket Booster (SRB) has a thrust of
approximately 3,300,000 pounds at launch.
(11/15/96)
The propellant mixture in each Space Shuttle Solid Rocket Booster
(SRB) consists of ammonium perchlorate (oxidizer, 69.9 percent
by weight), aluminum (fuel, 16 percent), iron oxide (a catalyst,
0.4 percent), a polymer (a binder that holds the mixture together,
12.04 percent), and an epoxy curing agent (1.96 percent).
(12/16/96)
During launch, the main engines of the Space Shuttle use liquid
hydrogen and liquid oxygen, which are stored in the large, expendable
central fuel tank.
(12/23/96)
During landing of a space shuttle, it takes approximately one
minute between touchdown of the wheels and wheelstop, the point
at which the shuttle comes to a complete stop.
(1/22/97)
Viking Lander 1 was originally scheduled to land on July 4, 1976,
just as Mars Pathfinder will land on July 4. However, the landing
was delayed and the site adjusted because the original site appeared
too hazardous in Viking Orbiter photographs. Landing occurred
July 20, 1976, seven years after Apollo 11 landed on the Moon.
(7/1/97)
Mariner 10 was the first spacecraft to encounter two planets (besides
Earth) on one mission. It flew past both Venus and Mercury in
the early 1970's.
(8/25/97)
ASTRONAUTS:
Who is the only astronaut to have flown into space on board all
five Space Shuttles (including Challenger)? The answer is Story
Musgrave.
(1/6/97)
The first American to eat food in space was Scott Carpenter aboard
the Mercury spacecraft Aurora 7 in 1962.
(5/22/97)
Stump your friends: who was the last astronaut to fly in space
alone in a spacecraft? For you space buffs who immediately thought
of Mercury astronaut Gordon Cooper, think again. It was Apollo
17 command module pilot Ron Evans, who circled the Moon alone
while astronauts Gene Cernan and Harrison Schmitt went to the
surface.
(6/21/96)
Only 12 humans have ever visited another world--all of them walking
on the Moon during brief stays between July 20, 1969 and Dec.
13, 1972 as part of the Apollo program.
(9/6/96)
MARS PATHFINDER:
The Mars Pathfinder rover, named Sojourner, is 63 cm (25 in) long
and 48 cm (19 in) wide, and weighs approximately 12 kg (25 lb).
(12/9/96)
Large channels and valleys on Mars are named after the name for
Mars in various languages. For example, Pathfinder landed at the
end of Ares Vallis. Ares is the Greek word for Mars.
(7/16/97)
SIZES & DISTANCE:
Size comparisons: About 1000 Earths would fit inside Jupiter,
and about 1000 Jupiters would fit inside the Sun.
(9/8/95)
Our Solar System, by virtue of its proper motion through our galaxy
(the Milky Way) is moving at a speed of 43,000 miles per hour
toward the globular cluster of stars known as M13 in the constellation
Hercules.
(11/20/95)
Some of the objects visible in Hubble Space Telescope images are
nearly four billion times fainter than the limits of human vision.
(1/31/96)
Comet Hyakutake's orbit will carry it over 1000 astronomical units
from the Sun before it once again heads back towards the Sun in
another 7,000 years (1 astronomical unit = the average distance
from the Earth to the Sun = 93 million miles = 150 million km).
Such large orbits are not unusual for long-period comets. For
comparison Pluto is on average 40 astronomical units from the
Sun and orbits the Sun once every 248 years.
(5/1/96)
The largest mountain in the Solar System is Olympus Mons on Mars.
At a height of over 26 km (16 mi.), it is nearly 3 times taller
than Mt. Everest. Olympus Mons is also enormous in its width:
600 km (360 mi.) across.
(6/14/96)
If you suspend three grains of sand in a large sports arena, such
as Madison Square Garden in New York, the arena will be more closely
packed with sand than our galaxy is with stars.
(12/4/97)
A beam of light travels just over twelve inches in one nano-second
(a billionth of a second). Some have suggested naming this unit
of distance the phoot.
(12/18/97)
The elements Carbon, Hydrogen, Oxygen, and Nitrogen - all crucial
to life - are found in roughly the same proportions in comets
and human beings.
(1/30/98)
At Voyager 1's present distance, sunlight is only one five-thousandth
as intense as it is on Earth. Radio signals from Voyager 1, traveling
at the speed of light (300,000 kilometers per second) take 9 hours
and 36 minutes to reach Earth.
(3/1/98)
The first experimental confirmation of Einstein's General Theory
of Relativity was made during the total solar eclipse of May 29,
1919. During an eclipse, bright stars become visible. Einstein
had predicted that gravity from the Sun would slightly bend the
path of starlight passing close to the Sun. Astronomers tested
this assertion by measuring the positions of several stars that
appeared close to the Sun during the 1919 eclipse. The deviations
in the observed positions of these stars due to the Sun's gravity
matched Einstein's predictions.
(3/15/98)
If all of the particles that make up Saturn's rings were gathered
together, they would form a sphere about 120 miles in diameter,
roughly the size of Saturn's seventh largest moon, Mimas.
(4/1/98)
The average distance between stars in the spiral arms of the Milky
Way galaxy is currently estimated to be seven light years, or
sixty-six trillion kilometers. This distance is equal to roughly
443,000 times the distance between the Earth and Sun.
(4/15/98)
THE SUN:
The Sun looks 1600 times fainter from Pluto than it does from
the Earth.
(1/10/96)
Comets' tails point away from the Sun at all times. Thus, when
a comet is moving away from the Sun, its tail is actually leading.
Comet tails are caused by dust and gas being lost from the comet
and then pushed away from the Sun by the solar wind (charged particles
moving out from the Sun) and by radiation pressure from the Sun.
(2/7/96)
The Sun is a fairly average star in terms of mass, temperature,
and size.
(2/14/96)
The Earth orbits the Sun at an average velocity of approximately
30 kilometers per second (18 miles per second). Planets closer
to the Sun travel faster in their orbits and planets further away
travel slower.
(04/03/96)
Sunspots appear dark because they are cooler than the surrounding
areas on the Sun, and therefore radiate less light and appear
"dark" relative to the areas around them. Sunspot temperatures
average about 3800 degrees versus 5800 degrees Celsius for the
average surface of the Sun.
(8/16/96)
Due to frequent collisions with subatomic particles, it takes
a typical gamma ray photon about one million years to travel from
the core of the Sun to its surface, even though gamma rays travel
at the speed of light (the gamma ray region of light has shorter
wavelengths than X-rays). By the time the photon that started
out as a gamma ray photon escapes the solar furnace, it has lost
so much energy through collisions that it emerges from the Sun's
surface as a photon of ordinary, visible light.
(1/1/98)