Speaker 1: Welcome to brain Stuff production of I Heart Radio. Hey
Speaker 1: brain Stuff, Lauren Bogelbaum. Here. You'd like to think you
Speaker 1: know your neighbors, but sometimes they'll catch you off guard.
Speaker 1: That diminutive world called Mercury is the first planet from
Speaker 1: our Sun, Venus's second, Earth is the third, and dear
Speaker 1: old Mars is number four common knowledge, but that numbering
Speaker 1: obscures certain truths. With its tight orbit around the Sun,
Speaker 1: Mercury can't ventures far away from Earth as Venus and
Speaker 1: Mars can during their larger orbits, so most of the time,
Speaker 1: Mercury is closer to Earth than any other planet, despite
Speaker 1: its place in the planetary lineup. And that's far from
Speaker 1: the weirdest thing about Mercury's travel patterns. Of all the
Speaker 1: planets in the Solar System, Mercury orbits our Sun at
Speaker 1: the fastest rate. It zips around our star with an
Speaker 1: average speed of around one hundred and five thousand, nine
Speaker 1: hundred miles per hour or a hundred and seventy thousand,
Speaker 1: five hundred kilometers per hour. The planet's namesake was a
Speaker 1: real speedster too. In Roman mythology, Mercury was the fleet
Speaker 1: footed god of commerce and communication, among other things. Recognizable
Speaker 1: by his winged sandals. Earth takes a little more than
Speaker 1: three hundred and sixty five days to loop around the sun.
Speaker 1: Mercury does the same thing in a fraction of the time.
Speaker 1: One Mercury in year is equal to a brisk eighty
Speaker 1: eight earth days vacationing there would be a disorienting experience
Speaker 1: on Mercury. The years may be quick, but the days
Speaker 1: are very long. The planet finishes a new rotation around
Speaker 1: its own axis once every fifty nine earth days, which
Speaker 1: means that every day on Mercury takes up almost exactly
Speaker 1: two thirds of every year. But due to some further strangeness,
Speaker 1: each day on Mercury isn't guaranteed to have a sunrise
Speaker 1: and a sunset. If we define a day not as
Speaker 1: a complete rotation of a planet around its axis, but
Speaker 1: rather as a solar day, a one complete day night cycle,
Speaker 1: the amount of time it takes our son to return
Speaker 1: to a specific point in the sky, then a single
Speaker 1: day on Mercury is a hundred and seventy six earth
Speaker 1: days long. That's the rough equivalent of two full Mercury
Speaker 1: in years. That's because Mercury's orbit is what we refer
Speaker 1: to as eccentric. No, not eccentric like Willy Wonka is eccentric.
Speaker 1: Eccentricity is a term astronomers used to describe the shape
Speaker 1: of a planet or moon's orbit. No planet orbits its
Speaker 1: star in a perfect circle. The extent to which had
Speaker 1: given orbit deviates from being circular is cold. It's eccentricity.
Speaker 1: If an orbit was one circular, would say it had
Speaker 1: an eccentricity of zero. Let The records show that Earth's
Speaker 1: orbit boasts an eccentricity of just zero point zero one seven,
Speaker 1: so it's almost a circle, but not quite. Mercury's orbit
Speaker 1: looks more squashed or elliptical. By comparison of all the
Speaker 1: planets in our beloved Solar system, Cury has the most
Speaker 1: eccentric orbit. The amount of space between this world and
Speaker 1: our Sun ranges from just twenty nine million miles to
Speaker 1: thirty six million miles during the course of its elliptical
Speaker 1: trip around the Sun. That's a forty six million to
Speaker 1: fifty eight million kilometers. Consequently, Mercury's travel speed increases as
Speaker 1: it gets closer to the star. Those changes in speed
Speaker 1: and distance from the Sun account for the strange solar days.
Speaker 1: When you view the Sun from some places on Mercury,
Speaker 1: it appears to freeze in place part way through its
Speaker 1: journey across the sky, then move backwards before going forward
Speaker 1: again in its route to the opposite horizon. Depending on
Speaker 1: where you are on the planet, this might mean that
Speaker 1: you get to sunrises in a row as the Sun
Speaker 1: dips back below the skyline before fully rising, or two
Speaker 1: sunsets in a row as it pops back up before
Speaker 1: fully setting, And of course all of this reeks havoc
Speaker 1: on the planet's temperatures on Mercury, they can range as
Speaker 1: high as eight hundred degrees fahrenheit that's four thirty celsius,
Speaker 1: or as low as negative two nine degrees fahrenheit or
Speaker 1: negative one eight celsius. As you could expect, the side
Speaker 1: of the planet that's facing the Sun at any time
Speaker 1: will be a good deal hotter, and on hot days
Speaker 1: we could all use some ice in NASA's Messenger spacecraft
Speaker 1: observed deposits of frozen water on Mercury. The ice was
Speaker 1: found at the bottoms of deep craters around the northern pole,
Speaker 1: which are protected from the sun all year long due
Speaker 1: to Mercury's lack of tilt around its axis of rotation.
Speaker 1: Earth tilts twenty three point five degrees on its axis,
Speaker 1: giving us seasons and exposing the poles to the Sun.
Speaker 1: But Mercury only tilts two degrees, meaning it spins almost
Speaker 1: completely upright, protecting its poles and preventing seasons from occurring.
Speaker 1: But back to that ice. Paradoxically, Mercury's hottest temperatures could
Speaker 1: be responsible for some of the ice that it possesses.
Speaker 1: Our Sun is constantly releasing charged protons and electrons in
Speaker 1: streams known as solar winds. Earth is shielded by a
Speaker 1: powerful magnetic field, which deflects many of these. Mercury has
Speaker 1: had a magnetic field of its own four around three
Speaker 1: point nine billion years. However, it's significantly weaker than the
Speaker 1: one we enjoy here on Earth. If a recent scientific
Speaker 1: model is correct, The intense heat of the planet's sun
Speaker 1: facing side triggers chemical reactions between solar wind particles and
Speaker 1: minerals buried in the soil. These are thought to create
Speaker 1: traveling water molecules that later become ice. Of all the
Speaker 1: frozen water on Mercury may have been generated this way,
Speaker 1: Mercury doesn't have any moons to call its own. As
Speaker 1: a matter of fact, With a diameter of just three thousand,
Speaker 1: thirty miles or four thousand kilometers, Mercury isn't much bigger
Speaker 1: than Earth's Moon easily. Mercury is the smallest planet in
Speaker 1: our Sun's orbit, yet evidence tells us that it used
Speaker 1: to be larger. Mercury is interesting to look at from
Speaker 1: a topographic standpoint. The thin atmosphere for his very little
Speaker 1: protection from asteroids, so impact craters are abundant. A single
Speaker 1: photo taken by the Messenger Probe in two thousand eight
Speaker 1: shows seven hundred and sixty three identifiable craters within a
Speaker 1: region of the planet's surface just a hundred and seventy
Speaker 1: two miles wide. That's two hundred and seventy six kilometers.
Speaker 1: It's traditional to name these craters after writers, given that
Speaker 1: eloquence is one of the realms of the mythological god Mercury.
Speaker 1: Truman Capote, Batteline la Engel, Betty Alver, and John Lennon
Speaker 1: are just some of the visionaries with their own namesake craters.
Speaker 1: The planet's face is also marked by fault scarps. These
Speaker 1: are cliff ridges that were first sighted on Mercury in
Speaker 1: the nineteen seventies. Some of the smaller ones appeared to
Speaker 1: be around just fifty million years old, making them geologically
Speaker 1: pretty young. Mercury itself formed around four point five billion
Speaker 1: years ago. Since then, its metallic core has been cooling
Speaker 1: down at a rapid pace, and as a result, the
Speaker 1: whole planet is currently shrinking. The diameter of mercury may
Speaker 1: have contracted by as much as eight and a half
Speaker 1: miles or fourteen kilometers over the eons. This has had
Speaker 1: a tremendous effect on the planet's rocky outer surface. Those
Speaker 1: previously mentioned fault scarps are born when crust materials break
Speaker 1: apart and press into each other, forcing some terrain upward.
Speaker 1: And because it's tectonically active in its own peculiar way, Mercury,
Speaker 1: like Earth, may experience surface level earthquakes. Mercury quakes will
Speaker 1: definitely be a topic worth investigating as we plot out
Speaker 1: future pro missions to our curious little neighbor. Today's episode
Speaker 1: was written by Mark Mancini and produced by Tyler clang Or.
Speaker 1: More on this and lots of other curious topics, visit
Speaker 1: how stuff works dot com. Brain Stuff is production of
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