- DAYS THAT CONSIST OF 24 HOURS
AND YEARS MEASURED BY 365 DAYS
ARE PRETTY STANDARD UNITS OF TIME FOR US HERE ON EARTH.
BUT ON THE PLANET CLOSEST TO THE SUN,
TIME TAKES ON A WHOLE NEW MEANING.
JUST HOW CAN THAT BE?
FIND OUT NEXT ON "REAL WORLD."
THE SUN'S PULL ON MERCURY HAS ACTUALLY SLOWED DOWN
THE ROTATION OF THIS SMALL PLANET.
AS A RESULT, ONE FULL DAY-- THAT'S NOON TO NOON--
TAKES ABOUT 176 EARTH-DAYS.
A DAY ON MERCURY WOULD LAST 4,2224 HOURS.
THAT'S A LONG TIME TO BE IN SCHOOL.
SO WHAT ELSE DO WE KNOW ABOUT MERCURY?
IT'S THE CLOSEST PLANET TO OUR SUN,
AND LIKE EARTH, IT'S TERRESTRIAL.
ITS TEMPERATURE RANGES
FROM A SCORCHING 427 DEGREES CELSIUS
WHEN THE SUN SHINES ON THE SURFACE
TO A FRIGID NEGATIVE 173 DEGREES CELSIUS
ON ITS NIGHT SIDE.
IN MANY WAYS, THE SURFACE OF MERCURY
IS MUCH LIKE THAT OF OUR MOON: HEAVILY CRATERED AND OLD.
BUT FOR EVERYTHING WE KNOW ABOUT MERCURY,
WE HAVE EVEN MORE QUESTIONS.
LET'S TALK TO PETER BEDINI
FROM THE JOHNS HOPKINS APPLIED PHYSICS LABORATORY
TO FIND OUT WHAT MAKES MERCURY SO MYSTERIOUS.
– THERE ARE SEVERAL THINGS
THAT CONFUSE US ABOUT THE PLANET.
IT IS VERY DENSE TO BEGIN WITH.
WE DON'T KNOW WHY.
IT DOESN'T HAVE AN ATMOSPHERE.
THERE ARE SO FEW PARTICLES IN THE ENVIRONMENT
THAT THEY CALL IT AN EXOSPHERE,
AND IT'S TENUOUS.
IT'S WISPY.
IT SORT OF MOVES A LOT.
IT'S VERY DYNAMIC.
MERCURY HAS A DYNAMIC MAGNETIC FIELD,
LIKE EARTH, BUT SMALLER,
AND THAT'S VERY UNUSUAL FOR A PLANET OF THAT AGE.
YOU'D THINK THAT THAT MAGNETIC FIELD
WOULD BE GONE ALREADY.
IT ALSO HAS SIGNS ON IT
THAT THERE WAS VOLCANISM ON THE PLANET.
SO THERE ARE A LOT OF MYSTERIES ABOUT THE PLANET.
- MERCURY'S POSITION SO CLOSE TO THE SUN
MAKES IT DIFFICULT TO STUDY.
NOT EVEN HUBBLE, OUR MOST POWERFUL SPACE TELESCOPE,
CAN LOOK AT MERCURY WITHOUT PERMANENTLY DAMAGING ITS OPTICS.
SO HOW CAN WE LEARN MORE ABOUT THIS UNUSUAL PLANET?
ONLY ONE NASA SPACECRAFT, MARINER 10,
HAS EVER VISITED THE PLANET MERCURY.
MARINER 10 WAS PROGRAMMED TO FLY BY MERCURY THREE TIMES
AND TAKE IMAGES OF THE HEAVILY CRATERED SURFACE.
UNFORTUNATELY, THE SPACECRAFT ESSENTIALLY SAW
THE SAME SIDE OF THE PLANET ON EACH FLYBY.
SCIENTISTS AND ENGINEERS SPENT THE NEXT DECADES
DEVELOPING NEW TECHNIQUES AND DESIGNING A SPACECRAFT
THAT COULD SURVIVE THE EXTREME CONDITIONS OF MERCURY.
NASA'S MESSENGER MISSION IS THE RESULT OF THEIR WORK.
MESSENGER-- OR THE MERCURY SURFACE,
SPACE ENVIRONMENT, GEOCHEMISTRY, AND RANGING--
IS THE FIRST MISSION TO MERCURY IN OVER 30 YEARS.
MESSENGER COMPLETED THREE FLYBYS OF MERCURY,
CAPTURING STUNNING NEVER-BEFORE-SEEN IMAGERY
OF THE SURFACE
BEFORE EVENTUALLY INSERTING ITSELF
INTO ORBIT AROUND THE PLANET.
A NEAT NAVIGATIONAL TECHNIQUE
THAT MESSENGER USED ON THE WAY TO MERCURY
WAS THE USE OF SOLAR RADIATION PRESSURE,
OR SOLAR SAILING, TO GUIDE THE PROBE'S TRAJECTORY.
- WE REALIZED THAT BY CHANGING THE ANGLES OF OUR SOLAR PANELS
OR TILTING THE BODY
AND EXPOSING DIFFERENT SURFACES TO THE SUN,
WE COULD ACTUALLY AFFECT WHAT PATH THE SPACECRAFT TAKES,
AND WE CAN TWEAK THE TRAJECTORY A LITTLE BIT.
THE BIGGEST SAVINGS THAT GIVES YOU
IS THAT YOU DON'T GO THROUGH THE RISK
OF OPERATING YOUR THRUSTERS.
WHENEVER YOU DO THAT,
IT'S ALWAYS RISKY TO THE SPACECRAFT.
SO BY USING SOLAR SAILING
AND JUST SAILING ON THE SOLAR PRESSURE
LIKE A SAILBOAT DOES IN THE WIND,
WE WERE ABLE TO DIRECT THE SPACECRAFT
WHERE WE WANTED IT TO BE.
- AND NOW THAT MESSENGER IS IN ORBIT,
THE SPACECRAFT WILL ALLOW US TO OBSERVE MERCURY
AS IT HAS NEVER BEEN SEEN BEFORE.
– WE'LL BE ABLE TO CHARACTERIZE ALL ASPECTS OF THE PLANET,
FROM THE INNER CORE
TO FIND OUT IF IT'S ACTUALLY LIQUID OR SOLID
AND IF IT'S DYNAMIC--
MAYBE THAT'S THE SOURCE OF THE MAGNETIC FIELD--
TO THE COMPOSITION OF THE SURFACE
BY USING A CAMERA SYSTEM THAT TAKES PICTURES
IN 11 DIFFERENT COLORS.
AND BY LOOKING AT THE DIFFERENT COLORS,
YOU CAN TELL THE COMPOSITION OF THE SURFACE.
WE HAVE A GAMMA RAY NEUTRON SPECTROMETER,
OR X-RAY SPECTROMETER,
THAT CAN TELL THE DIFFERENT ELEMENTS
THAT MAKE UP THE SURFACE.
AND WE HAVE A MAGNETOMETER, OF COURSE,
TO MEASURE THE MAGNETIC FIELD AND CHARACTERIZE IT.
- BUT WHY BOTHER STUDYING MERCURY?
HOW WILL KNOWING MORE ABOUT THIS PLANET
AFFECT US HERE ON EARTH?
A FAMILY PORTRAIT,
ONE OF MESSENGER'S NEWEST CONTRIBUTIONS,
HELPS US ANSWER THAT QUESTION.
THE 34-IMAGE MOSAIC OF THE SOLAR SYSTEM
GIVES SCIENTISTS A SNAPSHOT OF NEIGHBORING PLANETS
FROM MERCURY'S PERSPECTIVE.
THESE IMAGES HELP US UNDERSTAND THAT EARTH
IS A PART OF A PLANETARY FAMILY FORMED BY COMMON PROCESSES.
- THE WAY I THINK OF IT IS THAT THE SOLAR SYSTEM
IS LIKE A LARGE LABORATORY,
AND IT HAS IN IT A LOT OF PLANETARY BODIES
VERY SIMILAR TO EARTH.
MERCURY IS JUST ONE
THAT'S ONE OF THE MORE ELUSIVE ONES
THAT WE'RE NOW GOING TO FILL IN THAT GAP.
IT'S SORT OF AN EXTREME CASE OF THE TERRESTRIAL PLANETS.
IT'S CLOSEST TO THE SUN.
IT HAS THESE FEATURES I MENTIONED
LIKE THE MAGNETIC FIELD AND HIGH DENSITY.
AND BY LEARNING HOW IT EVOLVED
AND KNOWING WHAT WE KNOW ABOUT THE OTHER TERRESTRIAL PLANETS,
WE CAN LEARN A LOT MORE
ABOUT HOW EARTH ITSELF EVOLVED, HOW IT CAME TO BE.
- BY GATHERING DATA ABOUT MERCURY,
WE'LL BE ABLE TO GAIN SOME INSIGHT
INTO OUR OWN HISTORY.
AND WITH THE MESSENGER SPACECRAFT
HELPING US UNVEIL MERCURY'S MYSTERIES,
WHO KNOWS WHAT ASTRONOMERS WILL FIGURE OUT
BEFORE THE NEXT DAY ON MERCURY GOES BY?
SEE YOU NEXT TIME ON "REAL WORLD."