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SPECTRAL FIREWORKS | NASA
BY THE MERCURY ATMOSPHERIC AND SURFACE COMPOSITION SPECTROMETER (MASCS)
OUR JOURNEY
Let’s take our first step in this long journey toward the outer
reaches of our solar system.
Hello, Mercury!
EDITOR
Amanda Bell
February
CONTACT
Questions, comments, submissions, photos or just to say ‘hello’:
ObjView at NoCoAstro dot org
NoCoAstro
Join us for our monthly awesomely-nerdy astro talk:
Date: March 3rd, 6:15pm
Speaker: Dr. Daniel Baker
Topic: The Laboratory for Atmospheric and Space Physics (LASP):
Understanding Particles & Fields Throughout the Solar System
DID YOU KNOW…? All meetings are FREE & open to the public!
Just stop by the Fort Collins Museum of Discovery.
NOCOASTRO OUTREACH
12th, Saturday
14th, Monday
26th, Saturday
Fossil Creek Reservoir Skygazing, 7-9 pm
Poudre Learning Center Skygazing, 7:30-9:30 pm
Fossil Creek Reservoir Skygazing, 8-10 pm
February
MARCH
NOCOASTRO MEETING
MEET MERCURY
ORIGIN OF NAME: Named for the swift Roman god, Mercury. He has many titles, including god of commerce
and trade, god of thieves and even god of travel! He’s even considered to be messenger to the Roman gods, just like the
Greek god you may be familiar with: Hermes, messenger of the Olympic gods.
ATMOSPHERE TYPE: Mercury’s atmosphere, classified as a thin exosphere, is the thinnest atmosphere of all the
planets in our solar system. This tiny planet is über close to the sun and lacks any real protective atmosphere, so constant
bombardment by sunlight, solar wind and meteoroids wreaks havoc on the planet’s surface. Yet it may come as a surprise to
learn that it is actually the intense interaction between these solar particles and the planet’s magnetic field
that has helped Mercury retain any atmosphere at all. Intrigued?
MOONS: Nope. Nada. Zilch. Do you think any type of moon could survive this close to the sun?
SIZE: You probably already know that Mercury is the smallest planet in the solar system.
EQUATORIAL CIRCUMFERENCE: 9,525.1 miles [only 38% Earth circumference].
VOLUME: 14.6 trillion cubic miles [only 5.5% Earth volume].
MASS: 3.3 * 10^23 kg [only 5.5% Earth mass] & the least massive in the solar system.
MEAN DENSITY: 5.427 g/cm cubed [98.4% Earth density of 5.5 g/cm cubed]. Mercury is the
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second densest planet after Earth. The metallic core contributes at least 60% of the planet’s mass
- twice as much as the core of Earth, Venus or Mars! The core is 75% of the planet’s entire radius.
UNCOMPRESSED DENSITY: 5.3 g/cm cubed [4.4 g/cm cubed Earth uncompressed density]. This
measurement is the average density if the planetary materials were at zero pressure. Higher uncompressed
density indicates greater metal content. Now Mercury becomes the densest planet!
MAGNETIC FIELD: Historically, scientists thought Mercury’s diminutive size made it likely the planet’s core had
cooled long ago. Of course, this would’ve destroyed any planetary magnetic field. In the 1970s, however, scientists made a
breakthrough: an active magnetic field was found! Even though only1% the strength of Earth’s magnetic field, it still has a
remarkable affect on the planet as well as being a tool to help scientists understand planetary composition and planetary
changes over time. Just the fact the Mercury retains a magnetic field at all implies that its interior is at least still partially-molten.
NoCoAstro
SURFACE GRAVITY: 3.7 m/s squared [9.8 m/s squared on Earth]. Gravity on Mercury is about 38% that of Earth.
This means that for every 100 lbs you weigh on Earth, you would weigh only 38 lbs on Mercury! So, what is gravity, anyway?
SURFACE AREA: 28.9 million square miles [only 14.7% Earth surface area].
SURFACE: Mercury lacks a protective atmosphere and is covered with impact craters.
Mercury’s surface even has a massive crater basin 960 miles in diameter! Cliffs that reach
hundreds of miles high & hundreds of miles long cover the surface, created during the cooling
and contracting of Mercury’s surface over the billions of years since the planet’s formation.
Want to see it? NASA’S MESSENGER mapped Mercury's entire surface!
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PLANETARY COMPOSITION: Terrestrial. What does this mean?
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DISTANCE FROM SUN: 0.39 AU, about 36 million miles [1 AU is 93 million miles].
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ORBIT: True to its name, Mercury flies around the sun faster than any other planet - at about
37 miles per second at perihelion (fastest orbit) and 24 miles per second at aphelion. That averages to
about 105 thousand miles per hour! One year on Mercury (i.e., a complete orbit of the sun) occurs every 88 Earth days.
Though a full day/night cycle on Mercury is twice as long! That means one day takes two full years. How is this possible?
EQUATORIAL INCLINATION: Zero degrees. No, really.
PLANETARY ALBEDO: This is actually a complex subject but we can learn a lot from planet, satellite and asteroidal
albedos. Mercury has a planetary albedo of only 0.12, which means its surface does not reflect much light.
TEMPERATURE CHANGES: Mercury has the most extreme temperature fluctuations in the solar system!
MISSIONS / SPACECRAFT:
1974-1975: roughly half of Mercury’s surface is photographed in three flybys by Mariner 10.
2008-2009: MESSENGER performs 3 flybys.
NoCoAstro
2011-2015: MESSENGER then orbited Mercury until running out of fuel & crashing into Mercury’s moon-like surface.
February
Temperatures vary from a chilly -279 F at night to a scorching +801 F during the day, which is a whopping 1,100 degree
difference. Though don't be fooled, Mercury isn’t even the hottest planet in the solar system.
WHAT
EXACTLY IS
A PLANET?
REALLY? WATER
ON MERCURY?
HOW OLD ARE
THE PLANETS?
What is a planet & why is this even
important? Over time our ways of
categorizing astronomical phenomena
have changed, just as you would
expect.
Even though Mercury is uncomfortably
close to the sun, water ice exists at the
planet’s poles.
How is this possible, you ask?
Mercury’s orbital inclination is almost
zero, so its poles receive very little
direct sunlight. This means polar crater
floors remain permanently shadowed
— and permanently frigid.
Mercury is a land of extreme
temperatures. Could water ice actually
exist on its surface, so close to the sun?
Thanks to NASA’s MESSENGER
spacecraft, scientists have been able to
find and verify water ice on Mercury
using spectroscopy.
Now that we know what exactly
defines a planet (according to current
knowledge), let’s figure out the age of
our solar system — including the sun,
the planets and any other solar system
miscellany.
How do we know the age of the sun?
How do we know the age of planets in
our solar neighborhood?
When you think about it, the answer is
really quite simple… or is it actually
quite complicated?
You be the judge.
Did you know that at one time the sun
and moon were considered planets
while the Earth wasn’t? When did our
hazy definition(s) of what makes a
planet begin to create problems?
As our knowledge continues to
expand, how will our other definitions
and categories become more specific
or even change completely? Let's ask
NASA.
February
A S T R O N O M Y G U I D E : S U M M E R 2 016
Pickett Astronomy Weekend:
J a m e s t o w n , Te n n e s s e e . A p r i l 1 - 3 . C l i c k .
OzSky Star Safari: Coonabaran, New South
Wales, Austr alia. Apr il 2-9. C l i c k .
Northeast Astronomy Forum:
S u f f e r n , N e w Yo r k . A p r i l 9 - 1 0 . C l i c k .
38th Annual Texas Star Party:
RTMC Astronomy Expo:
B i g B e a r C i t y, C a l i f o r n i a . M a y 2 6 - 3 0 .
Click.
February
F o r t D a v i s , Te x a s . M a y 1 - 8 . C l i c k .
WE
WA
NT
TO
PRESIDENT
HE
AR
Trevor Moriarty: pres at NoCoAstro dot org F R
OM
YO
VICE PRESIDENT
U!
Bob Michael: vp at NoCoAstro dot org
TREASURER & OUTREACH
Greg Halac: treas at NoCoAstro dot org
SECRETARY
Dave Karp: sec at NoCoAstro dot org
NEWSLETTER EDITOR
February
Amanda Bell: ObjView at NoCoAstro dot org
WEBSITE
Robert Arn: web-edit at NoCoAstro dot org
NoCoAstro
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