[upbeat music]
- "OUR WORLD."
- YOU'VE ALL SEEN THE MOON IN THE SKY, RIGHT?
ALTHOUGH IT MAY NOT LOOK THE SAME EVERY NIGHT,
IT IS EARTH'S ONE AND ONLY MOON.
BUT DID YOU KNOW THAT OTHER PLANETS HAVE MOONS TOO?
IN FACT, THERE ARE OVER 300 MOONS IN OUR SOLAR SYSTEM.
ALL OF THE PLANETS HAVE MOONS ORBITING THEM
EXCEPT FOR MERCURY AND VENUS.
THE INNER PLANETS HAVE FEWER MOONS ORBITING THEM
THAN THE OUTER PLANETS.
GAS GIANTS LIKE SATURN AND JUPITER
HAVE OVER 50 MOONS ORBITING EACH ONE OF THEM.
AS ASTRONOMERS USE BETTER AND BETTER TELESCOPES
AND SEND OUT MORE SPACE PROBES,
THEY CONTINUE TO FIND EVEN MORE MOONS.
AND THESE MOONS COME IN ALL DIFFERENT SIZES.
SOME MOONS ARE REALLY HUGE, LIKE JUPITER'S MOON GANYMEDE.
THIS MOON IS SO BIG
THAT IT'S ACTUALLY BIGGER THAN THE PLANET MERCURY.
OTHER MOONS ARE REALLY SMALL, LIKE MARS' MOON DEIMOS.
IT'S ONLY 12 KILOMETERS IN DIAMETER.
SOME MOONS, LIKE JUPITER'S EUROPA,
ARE REALLY INTERESTING TO SCIENTISTS AND RESEARCHERS.
HERE'S DR. JAMES GREEN,
DIRECTOR OF PLANETARY SCIENCES AT NASA,
TO TELL US A LITTLE BIT ABOUT EUROPA.
- WELL, WHAT'S ON THE SURFACE OF EUROPA IS ICE.
SO WHAT HAPPENS TO THE ICE OF EUROPA?
THE PULL THAT JUPITER PUTS ON EUROPA
EVAPORATED THE ICE AWAY,
AND YOU'RE LITERALLY LOOKING AT WHAT'S LEFT.
BUT WHAT IT'S DOING IN THE INSIDE
IS MELTING THE ICE.
WE NOW KNOW THERE'S MORE WATER ON EUROPA
THAN THERE IS ON THIS PLANET.
- COOL.
I LEARNED HOW SMALL OBJECTS IMPACT BIG OBJECTS IN SPACE
AND LEAVE HUGE CRATERS, LIKE THOSE FOUND ON OUR MOON.
THAT'S THE SAME REASON SATURN'S MOON MIMAS
HAS A HUGE CRATER ON ITS SURFACE.
AND LOOK AT ALL THE CRATERS ON JUPITER'S MOON CALLISTO.
SATURN'S MOON TITAN HAS REALLY MADE RESEARCHERS CURIOUS.
HERE'S DR GREEN AGAIN TO TELL US MORE.
- BUT WITH CASSINI, THESE ARE THE IMAGES WE'RE BRINGING BACK.
THESE REGIONS, THESE DARK REGIONS,
WE NOW KNOW ARE LIQUID.
TITAN IS THE ONLY OTHER OBJECT BESIDES THE EARTH
IN OUR SOLAR SYSTEM THAT HAS LIQUID ON ITS SURFACE.
AND THAT LIQUID IS NOT WATER.
IT IS METHANE AND ETHANE.
IT'S A COMPLETELY DIFFERENT WORLD.
AND IN FACT, RIGHT NOW, TODAY, IT IS RAINING METHANE
IN THE SOUTHERN HEMISPHERE OF TITAN.
IT HAS A HYDROLOGICAL CYCLE MUCH LIKE THE EARTH
OF EVAPORATION, CONDENSATION, RAIN.
THAT CYCLE THAT WE'RE SO FAMILIAR WITH
IS GOING ON RIGHT NOW IN THIS MOON TITAN.
- RAIN ON A MOON?
I THOUGHT THAT ONLY HAPPENED ON EARTH.
AND WHAT ABOUT ENCELADUS?
I HEARD THAT'S ANOTHER REALLY COOL MOON OF SATURN.
- AND WHEN WE LOOK AT ENCELADUS CLOSELY,
WE FIND IN THE SOUTHERN HEMISPHERE
HUGE GEYSERS OF WATER BEING POURED OUT.
IS THAT COMING FROM AN UNDERGROUND OCEAN?
IS IT COMING FROM A LAKE?
WHAT IS THE PROCESS THAT DOES THAT,
AND IS THERE POTENTIAL FOR LIFE EVEN ON THIS DISTANT REGION
SO, SO VERY FAR AWAY FROM THE EARTH?
- WOW, THERE MIGHT EVEN BE LIFE ON ONE OF SATURN'S MOONS.
WHO KNEW THERE COULD BE RAIN OR VOLCANOES OR ICE
OR MAYBE EVEN LIQUID WATER
ON THESE MOONS IN OUR SOLAR SYSTEM?
I THINK THE MOONS ARE JUST AS INTERESTING
AS THE PLANETS ARE.
WHO KNOWS WHAT ELSE WE'LL FIND OUT ABOUT THEM?
HEY, DON'T GET LEFT BEHIND.
YOU CAN FOLLOW THE NASA MISSIONS TO OTHER WORLDS
BY VISITING NASA'S SOLAR SYSTEM WEBSITE.
AND THE NEXT TIME YOU LOOK UP AT THE NIGHT SKY,
JUST REMEMBER THAT SOME OF THE THINGS
YOU CAN SEE FROM OUR WORLD
JUST HAPPEN TO BE MOONS ORBITING OTHER PLANETS.
- "OUR WORLD."