Tag: MESSENGER

Mercury A to Z: NASA Missions to Mercury

~ J.S. Pailly ~ 4 Comments

Hello, friends!  We are halfway through this year’s A to Z Challenge.  I have to admit when I picked the planet Mercury as my theme for this year’s challenge, I was a little worried I wouldn’t be able to find enough material for a full alphabet worth of posts.  But Mercury has not disappointed me.  There are more than enough Mercury facts to cover!  In today’s post, N is for:

NASA MISSIONS TO MERCURY

Which planet is closest to the Sun?  More often than not, the answer is probably Mercury.  That may seem counterintuitive, since the orbital path of Venus (the 2nd planet) lies between the orbital paths of Mercury (the 1st planet) and Earth (the 3rd planet).  But consider it this way: every time Venus and Earth happen to be on opposite sides of the Sun, Mercury is somewhere in between.  So on average, Mercury ends up being the closest planet to Earth more often than Venus, Mars, or any other planet.

And yet, despite the fact that Mercury is so close to Earth so much of the time, Mercury is still one of the absolute hardest places for Earth-launched spacecraft to reach.  The problem is the Sun.  The Sun is very big, and the gravitational pull of the Sun is very strong.  For our purposes, imagine that the Sun is “down,” and you’ll start to see what the problem is.  Flying to Mercury is an awful lot like falling toward the Sun.

Now I do want to acknowledge that I’m glossing over a whole lot of technical details here.  The purpose of this blog post is not to teach you the science and mathematics behind orbital mechanics.  All I want is to give you a small taste of what makes flying to Mercury so very challenging, so that you can better appreciate the amazing accomplishments of NASA’s Mariner 10 and MESSENGER Missions.

MARINER 10

NASA’s original plan for Mariner 10 was to aim carefully and fly by Mercury one time.  A certain Italian astronomer had a better idea, involving a never-before-attempted gravity assist maneuver near Venus.  This tricky maneuver allowed Mariner 10 to perform three flybys of Mercury for the price of one.

Gravity assist maneuvers, where a spacecraft uses a planet’s gravity to make a “for free” course adjustment, are standard practice in spaceflight today, but Mariner 10 was the first to ever attempt such a thing.  Mariner 10 was also the first spacecraft to visit two planets, collecting some data about Venus before continuing on its way to Mercury (Mariner 10 was also lucky enough to collect data from a nearby comet—another first in space exploration).

Mariner 10 flew by Mercury in March of 1974, September of 1974, and March of 1975.  During those three encounters, Mariner 10 discovered Mercury’s magnetic field and Van Allen radiation belt.  Mariner 10 also discovered Caloris Basin, Kuiper Crater, and many other important surface features.  Unfortunately, only half of the planet was in daylight during Mariner 10’s three flybys, and it was always the same half of the planet, so the other half of Mercury remained unseen and mostly unknown for decades thereafter.

Shortly after Mariner 10’s third flyby of Mercury, the spacecraft ran out of fuel for attitude control.  Without attitude control, the spacecraft couldn’t keep its communications system pointed toward Earth.  So before contact was lost, mission control ordered the spacecraft to shut down.  The now defunct spacecraft is still, presumably, orbiting the Sun somewhere near the orbit of Mercury.

MESSENGER

MESSENGER is an acronym for MErcury Surface, Space Environment, Geochemistry, and Ranging.  The name is also a reference to Mercury’s role in Roman mythology as the messenger of the gods.  The MESSENGER Mission was funded through NASA’s Discovery Program, a highly competitive program for space missions that can be done on a tight and highly-restrictive budget.

MESSENGER launched on August 3, 2004.  Unlike Mariner 10’s series of flybys, the plan for MESSENGER was to enter orbit of Mercury.  This required a much longer and more intricate flight trajectory, with one gravity assist maneuver at Earth, two at Venus, and a series of three maneuvers at Mercury to help match Mercury’s orbital velocity.  MESSENGER achieved Mercury orbit on March 18, 2011, after seven-plus years of travel.

Over the next four years, MESSENGER photographed the entire surface of Mercury (including the half of the planet Mariner 10 couldn’t see), continued to study Mercury’s magnetic field, and revealed Mercury’s internal structure through a process called gravity mapping, which involved measuring subtle variations in a planet’s gravitational field.  Oh, and who could forget this?  MESSENGER also discovered water on Mercury.  Believe it or not, there is water (frozen as ice) inside craters around the north and south poles of Mercury.

In early 2015, MESSENGER ran out of fuel, and the spacecraft’s orbit around Mercury began to deteriorate.  On April 30, 2015, MESSENGER finally crashed into the planet’s surface, giving the most heavily cratered planet in the Solar System one additional crater.

WHAT’S NEXT?

The work of NASA’s Mariner 10 and MESSENGER Missions will be continued by BepiColombo, a collaborative mission by ESA (the European Space Agency) and JAXA (the Japanese Aerospace eXplotation Agency).  I wrote about BepiColombo in a previous post.

Now I want to correct something I’ve been saying about BepiColombo in previous posts.  I’ve said that BepiColombo will arrive at Mercury in 2025; that’s not quite right.  BepiColombo will enter Mercury orbit in 2025, but much like MESSENGER, BepiColombo needs to perform several gravity assist maneuvers near Mercury first.  Two of those gravity assists have already happened, and during those maneuvers, BepiColombo already started snapping photos and gathering science data.

So every time this month that I said only two spacecraft have ever visited Mercury, that was incorrect.  BepiColombo has already become Mercury’s third visitor.

WANT TO LEARN MORE?

NASA has posted some nice articles about Mariner 10, MESSENGER, and BepiColombo on one of their educational websites.  Click these links to check them out:

Mercury A to Z: Graphite

~ J.S. Pailly ~ 15 Comments

Hello, friends!  For this year’s A to Z Challenge, I’m giving you a guided tour of the planet Mercury, perhaps the Solar System’s most under-appreciated planet.  In today’s post, G is for:

GRAPHITE

I did not know this prior to doing my research for this A to Z series, but apparently Mercury is the least reflective, darkest colored planet in the Solar System.  For a long time, scientists assumed Mercury’s dark color must have something to do with iron.  Thanks to the planet’s unusually high density, we know that Mercury is an iron-rich planet, after all.  However, NASA’s MESSENGER spacecraft was unable to detect significant amounts of iron on the planet’s surface.

After rethinking their assumptions and reanalyzing MESSENGER’s data, scientists now believe that Mercury’s crust might be covered in carbon, specifically carbon in the form of graphite.  The same material used in pencils.  So how did this happen?  How did Mercury get covered in graphite?

Let’s go back in time.  Billions of years ago, when the Solar System was still forming, Mercury would have been just a giant ball of liquid magma.  During that time, heavier elements, like iron, would have sunk down toward the center of the planet; meanwhile, lighter elements, like carbon, would have floated up toward the planet’s surface.  As a result, when the planet started to cool off and solidify, a significant amount of carbon would have been incorporated into the planet’s crust.

Something similar must have happened on Venus, Earth, and Mars; however, Venus, Earth, and Mars continued to be geologically active for a long time after they formed (fun fact: Earth is still geologically active today!).  Mercury didn’t.  So while volcanic eruptions, plate tectonics, and the like allowed Venus, Earth, and Mars to transform their carbon rich surfaces into more mineralogically mixed planetary crusts, Mercury’s crust stayed more or less the same.

I don’t want to make it sound like Mercury didn’t try.  Some amount of volcanic activity did happen on Mercury, long ago.  And in some cases, asteroid impacts punched through the planet’s crust, causing lava to spill out onto the planet’s surface (remember my post on Caloris Basin?).  But even in regions where Mercury’s original crust has been resurfaced by lava, small asteroid impacts have re-exposed the graphite layer underneath.  Those asteroid impacts have also scattered graphite dust over the surfaces around craters.

Based on what I read, it seems that NASA’s MESSENGER spacecraft was not well equipped to study the graphite on Mercury.  And why would it be?  When MESSENGER was launched, no one knew the graphite was there, and given how expensive space exploration is, you don’t want to load up a spacecraft with equipment that you don’t think you’ll need.  And honestly, who would have expected to go to another planet and find the place is covered in pencil lead?

Anyway, hopefully ESA/JAXA’s BepiColombo Mission will be able to follow up on this when it arrives in Mercury orbit in 2025.

WANT TO LEARN MORE?

Here’s an article from The Conversation about the discovery of graphite on Mercury.

And here’s the original research paper reporting on the discovery.

Also, if it’s true that Mercury is covered in graphite, then the force of asteroid impacts might have turned some of that graphite into diamonds.  Click here to learn more about that.

Colonizing Mercury: How to Live There

~ J.S. Pailly ~ Leave a comment

If you hunger for a quaint, frontier life far from the noise and bustle of modern society, then moving to Mercury might be for you. Maybe. At first glance, Mercury appears to be the most godforsaken planet in the Solar System. But—assuming you can get there—living there might not be so bad.

One thing you and your fellow colonists won’t have to worry about is energy. You’ll have all the solar power you could ever need. In fact, you might get a little too much solar power. The MESSENGER space probe, currently orbiting Mercury, actually angles its solar panels away from the Sun to prevent overheating.

What about air and water? Turns out certain craters near Mercury’s north pole contain plenty of water in the form of ice. Colonists living in and around these craters would have easy access to that water, and they’d be able to extract oxygen from the water as well.

Fe08 Polar Craters
Water ice lies in Mercury’s polar craters, safely concealed from the Sun’s harsh glare.

 

Despite Mercury’s proximity to the Sun, keeping cool isn’t impossible. Thanks to a simple sunshade and a series of “diode heat pumps,” MESSENGER’s computers operate at room temperature. In fact, if you’re living inside one of those polar craters, perhaps in some sort of subterranean bunker, your bigger concern should be how to keep warm.

But is a Mercurial colony economically feasible? Well, it’s a safe bet that helium-3 will be the optimal fuel source for any futuristic, Solar-System-spanning civilization. Being so close to the Sun, Mercury has loads of helium-3, so establishing a colony there might someday be highly lucrative.

Believe it or not, some people actually want to live on Mercury. They even argue that colonizing Mercury will be easier and cheaper than colonizing Mars. I doubt that, but after all the research I’ve done for this post and the post before it, I can at least agree that colonizing Mercury isn’t as crazy as it might seem.

P.S.: One of those craters near Mercury’s north pole is named after J.R.R. Tolkien. I can only assume that in the future, any subterranean dwellings in that region will be colloquially known as Hobbit holes.

Links

Colonizing Mercury, Could It Be Done from Colony Worlds.

First Photos of Water Ice on Mercury Captured by NASA Spacecraft from Space.com.

“The Hobbit” Author Gets a Crater on Mercury from Universe Today.

Colonizing Mercury: How to Get There

~ J.S. Pailly ~ 4 Comments

In several recent posts (here and here), I’ve said that nobody wants to live on Mercury. It’s too hot. It’s also too cold, and there’s no air, et cetera, et cetera. But apparently some people do want to colonize Mercury. If you’re one of them, your first obstacle is getting there.

Only two spacecraft have ever visited the First Rock from the Sun, and the process of getting there was not exactly straightforward. (Get it! No? You will in a minute.) The problem is the Sun.

The Sun is massive, and so is its gravity. By comparison, Mercury’s gravity is minuscule, so trying to achieve Mercurial orbit requires guts, pinpoint accuracy, and a little unconventional thinking.

The MESSENGER spacecraft did it by taking an indirect course through the inner Solar System. It looped past Earth once, Venus twice, and Mercury three times before settling into a safe planetary orbit.
https://www.youtube.com/watch?v=Ownzbb1mKxs
This long, spiraling voyage took six years. A trip to Pluto would take just as long even though Pluto is five times farther away.

Barring some ginormous advances in anti-gravity technology, any effort to colonize Mercury would most likely have to follow MESSENGER’s convoluted path to get there.

Of course, living on Mercury presents a whole other set of challenges. More on that in Wednesday’s post.

Links

How Long Does It Take to Get to Mercury? from Universe Today.

NASA Probe Becomes First Spacecraft to Orbit Mercury from Space.com.

Mercury Orbit Insertion Press Kit from NASA.

Earth Photobombs Saturn

~ J.S. Pailly ~ 3 Comments

Back in July, NASA’s Cassini spacecraft happened to be in perfect alignment with Saturn and the Sun (the technical term for that is syzygy, by the way!).  This allowed Cassini to take an amazing snapshot of a Saturnian eclipse.  If you haven’t seen this picture yet, you really need to check it out (click on the image below to see a larger, more detailed version).

IDL TIFF file
Click image to see full scale version, courtesy of Astronomy Picture of the Day.

Cassini has taken other pictures of Saturn eclipsing the Sun, but this one is particularly special.  Far off in the background, you can see a tiny, blue speck; namely, Earth.  If you look closely, you might be able to see the even tinier speck beside it: our beloved Moon.  Venus and Mars are also in the photo, meaning that in this one picture you can see half the planets in the Solar System all at once (or almost half, depending on your opinion about Pluto).

But wait, there’s more!  If you click on the image and view the full-scale version, you should be able to find at least three of Saturn’s moons.  Just below Saturn and slightly to the left, you should see a small, tan-colored moon which I’m guessing is Titan, and there’s another moon nearby that’s almost certainly Enceladus (the geysers give it away).  A third moon is located in the upper right, but most of it is in shadow so I can’t guess what its name might be.

We know for a fact that there is life—lots and lots of life—crammed onto that one tiny, blue speck, but we Earthlings might not be alone.  According to recent theories, there are four other places in the Solar System that might be able to support life: Mars, Europa (a moon of Jupiter), Titan, and Enceladus.  So it’s possible that this picture doesn’t just show a bunch of cool planets and moons.  It may also be our first group photo with the Martians, Titanians, and Enceladians.  This picture might be the first to show all the life bearing worlds of the Solar System together (or almost all of them—sorry, Europa—we’ll try to squeeze you in next time).

As you can tell, I’ve spent an embarrassingly large amount of time studying this image and thinking about what it means.  It’s stuff like this that keeps me from getting too bogged down with earthly concerns.  Pictures like this remind me that I’m a citizen of a much bigger, much wider universe.  So I want to send a big thank you to the Cassini spacecraft for sending back such an awesome photo!

P.S.: Click here for another cool picture of Earth and the Moon.  This one’s close enough that we’re not reduced to a tiny, nearly invisible speck, but still far enough away to show how truly small our planet is.  The picture was taken by the MESSINGER spacecraft while on route to Mercury.

Vacation on Mercury

~ J.S. Pailly ~ Leave a comment

If you’re looking for someplace warm for your next vacation, it doesn’t get much warmer than Mercury.  The problem is getting there.  Mercury is so close to the Sun that it’s easy for your spaceship to get lost in the Sun’s gravity.  The MESSENGER Probe, currently in orbit of Mercury, took years to get there not because of the distance but because it had to approach at just the right angle with just the right velocity, or else it would’ve crashed into the Sun.

When you finally reach Mercury, you might experience some serious jet lag.  According to NASA, one Mercury day is equal to 58.6 days on Earth, and a Mercury year is about 88 Earth days long.  Also, because of Mercury’s proximity to the Sun, the planet is in a slight space-time warp, due to Relativity.  In fact, the space-time distortions of Mercury’s orbit were one of the first clues supporting Einstein’s Theory of Relativity.

Remember to bring sunscreen.  The daytime temperature is roughly 800 °F, and there’s no ozone layer to protect you from those UV rays.  In fact, there’s not much atmosphere at all, so you may want to pack some oxygen too.

For more information before you plan your trip, check out NASA’s website and be sure to visit Mercury Today for the latest news on the First Planet.  You can also read Ben Bova’s science fiction novel Mercury, which I’m sure is 100% accurate.

About the cartoon: Get it?  The planet Mercury is really hot, so it’s taking its temperature with a mercury thermometer.

Mysteries of Mercury

~ J.S. Pailly ~ Leave a comment

The MESSENGER Probe has been in orbit of Mercury for about three months now, and its already unraveling some of the tiny planet’s biggest mysteries.  Just getting a probe to Mercury was a challenge, due to the proximity of the Sun, so until now we’ve had surprisingly little information about that particular planet.

Some of the things MESSENGER is investigating include Murcury’s volcanic activity, its magnetic field, and the possibility that, deep within some of its craters, there might be water ice.  In the spirit of science fiction, here are some other things it might find.

  • In addition to water at the bottom of those craters, perhaps there are tunnel entrances leading to a labyrinth of underground caves where alien life could exist.
  • Evidence that Mercury is not a planet but an abandoned, Death-Star-like spaceship.
  • Analysis of the surface reveals that it is Mercury, not the Moon, that is made of cheese.  Unfortunately, because of the heat generated by the Sun, the cheese is overcooked and completely inedible.

What are your theories?  What do you think we might find on Mercury?