Much of our information about this eruption has come from the European Space Agency’s Envisat satellite, which is a state-of-the-art meteorological instrument in orbit around Earth.  In this article, we’ll take a look at this device, the awesome phenomenon of the eruption itself, and the larger scientific value of studying events like this.

In the study of our planet, we humans are hampered by our very smallness, and the brevity of our lives.  To us, 1821 seems like a long time ago.  If a volcano waits that long between eruptions, we might get a false sense of security- but the people of Iceland have been watching volcanoes for a long time, and they know better.  They know that to a volcano, 1821 was only yesterday.  It’s just long enough for the pressure to build up again- and Iceland has an awful lot of pressure.

The reason is a stroke of amazingly bad luck.  This poor island is the only piece of real estate on the planet that exists directly over not one, but two, of Earth’s pressure vents.

One of these pressure vents is the boundary between two tectonic plates.  America is on one plate and Eurasia is on another.  These plates literally float on the liquid rock of the planet’s mantle, and at the boundary between the two, that liquid rock sometimes seeps through.

Now, there is also another formation called a hotspot, which is made by a huge column of molten rock welling up under the surface.  As you might imagine, this makes the rock above the column bulge up.  If it happens on the ocean floor, it can make an island.

Now, just imagine these two things happening in the same place: a hotspot makes an island right over the boundary between two tectonic plates.  This incredibly unlikely coincidence would create an island which was constantly leaking magma and gases from deep within the Earth.

OK, you don’t have to imagine it; you can just look at the globe.  The winner of our Unluckiest Island in the World Award is Iceland, which is created by an enormous hotspot, and also exactly straddles the Mid-Oceanic Ridge which separates the American tectonic plate from the Eurasian one.  At some unknown time in the future, that column of magma under the hotspot is going to blow, and the resulting eruption will be one of the most destructive events in the life of the planet.

To their great credit, the Icelandic people have made good use of this energy.  Iceland currently leads the world in the generation of electricity by geothermal means.  Sitting on top of a hotspot does have its advantages.

And there’s another good side to all this, if you’re a planetary scientist: Iceland gives you a lot to study.  The island is like a geothermal laboratory where the workings of a planet can be studied in detail.  By looking at Iceland, we can see the interplay of forces that also exist on other small, rocky bodies.  Volcanoes, both active and extinct, have been observed on several other worlds in the solar system.  For instance, Mars has a huge mountain called Olympus Mons (appropriate, don’t you think?) which is a volcanic cone so high that its peak is outside the atmosphere.  Volcanoes have also been observed on some of the system’s moons, and recent evidence indicates that Venus may have active volcanoes, too.  This is one of those lucky instances where Earth presents us with an analog of something that exists on other worlds.  By studying the one we’ve got here, we can, in a way, study the ones out there, too.  The things that we learn about planetary forces and how they interact will also be true on those other worlds.

And that brings us to Envisat.  This satellite, which was designed for studying the weather, has proven invaluable in observing the Eyjafjallajoekull eruption.  This is a good example of a spacecraft that has been adapted to a job which is beyond its originally intended design.

Envisat, launched by the European Space Agency in 2002, is the largest Earth-observing spacecraft ever built.  It is equipped with 10 instruments which perform both optical and radar observations of Earth and give a wealth of data on how the planet works, including factors contributing to global warming.

While a list of all the devices on Envisat would be tedious and exhausting, we can take a look at the two most important ones, both of which are new pieces of technology:

The biggest single instrument on Envisat is called Advanced Synthetic Aperture Radar (ASAR).  It is a significant improvement over any previous meteorological radar unit, with enhanced ability in coverage, range of incidence angles, polarization and modes of operation.  The elevation of the radar beam can be steered, and the observations can be made in swaths of varying width, either 100 or 400 km wide.

MERIS, the Medium Resolution Imaging Spectrometer, is designed to measure the solar radiation reflected by the Earth.  It can observe the entire planet in three days.  Its primary mission is studying the color of the water in oceans and coastal areas.  From this it is possible to derive measurements of chlorophyll pigment concentration in algae, suspended sediment concentration and aerosol loads over marine seas.  In addition, it is used for atmospheric and land monitoring.

Envisat has given us a view of this event that we have never had for any other volcanic eruption.  The satellite, of course, was specifically calibrated for measuring the characteristics of clouds, and a new algorithm had to be devised to adapt it to the volcanic ash plume.  This has been working very well, providing detailed information on the movement, altitude and size of particles involved.  Since the blanket of ash that is spread by an eruption is one of its most destructive aspects, knowing how it moves and where it settles will be of great importance in preparing for future events of this type, and in understanding volcanoes everywhere.

And by studying this one, we are studying a scaled-down model of Olympus Mons on Mars, the volcanoes of Jupiter’s moon Io, and all the other volcanoes of the solar system.  How convenient!

One good thing: amazingly, there have been no casualties from this eruption.  Several hundred households in the vicinity of the volcano had to be evacuated, but all survived.

At this writing (April 24) the eruption is still happening.  The initial plume of ash has subsided enough for air traffic to resume, but it will take days or even weeks to get all those stranded passengers to their destinations.  A news report from two days ago (see sources) says that there are still ominous rumblings coming from the volcano.  Events of this type sometimes continue sporadically for some time, so we may not have heard the last from this one.

Whatever happens, Envisat will be there to watch it.  Thanks to the ESA and their outstanding satellite, future vulcanologists will have an in-depth profile of this eruption to study for years to come.

Sources:

“ESA Observing the Earth: New Satellite Image of Volcanic Ash Cloud, 15 April 2010″ at website of the European Space Agency:  esa.int/esaEO/SEMFYR9MT7G_index_0.html

“ESA Observing the Earth: New Satellite Image of Ash Spewing From Iceland’s Volcano, 19 April 2010″ at website of the European Space Agency:  esa.int/esaEO/SEMM16XN58G_index_0.html

“ESA Missions Observing the Earth: Envisat Overview” at website of the European Space Agency:  esa.int/esaEO/SEMWYN2VQUD_index_0_m.html

“Tremors on the Increase at the Eyjafjallajoekull Volcano” at newspublic:  news-public.com/index.php?option=com_content&view=article&id=1707:tremors-on-the-increase-at-the-eyjafjallajoekull-volcano&catid=34&Itemid=65

“Icelandair reschedules Flights out of Glasgow Despite Keflavik Airport Closure” in IceNews: News From the Nordics 24 April 2010:  icenews.is/index.php/2010/04/24/icelandair-reschedules-flights-out-of-glasgow-despite-keflavik-airport-closure/

The idea of putting a telescope in space, above the blurring effects of Earth’s atmosphere, was first proposed in 1923 by Hermann Oberth, one of the pioneers of rocketry. Unfortunately, Oberth was one of those true visionaries whose imagination far outpaces the technology of his age, and the idea was ignored at the time- but in 1946, Lyman Spitzer, an American astrophysicist, wrote a paper proposing the same thing.

Spitzer became a crusader for his idea. Over the coming decades, his quiet advocacy was the main force behind a whole generation of orbital observatories, including the Copernicus Observatory and the Orbiting Astronomical Observatory. It was his authoritative voice that spurred NASA to approve the Large Space Telescope project in 1969. Unfortunately, Spitzer’s original proposal got downsized due to budget problems, and took some years to get off the ground. (Another bad pun!)

In 1974, the planning group for the project made a modification to the original idea: the satellite would carry not just one telescope, but a number of instruments which could be removed and changed. When new devices were developed, they could be added onto the existing structure, so the satellite would not become obsolete when new technology was invented.

In 1975, NASA and the European Space Agency began a collaborative effort that would eventually become the Hubble Space Telescope. Congress approved funds for the project in 1977.

NASA first planned to launch the telescope in 1983, but as often happens in space science, there were delays. The entire optical assembly was not put together until 1984, and the whole spacecraft was not assembled until 1985. However, 1983 did have one important event: that was the year when the name of the device officially became the Hubble Space Telescope, in honor of Edwin Hubble, the imminent American astronomer.

The revised launch date was in October, 1986- but then disaster struck. The space shuttle Challenger exploded just one minute into its flight, and all shuttle flights were cancelled for the indefinite future. Since Hubble was supposed to be launched from the shuttle, nobody knew when or if it would go up.

Years passed; shuttle flights were eventually continued. Planning for the Hubble telescope was resumed.

All the planning finally came to fruition in 1990. There was quite a bit of hype preceding the launch; in a world where astronomy rarely gets the front page, Hubble was as famous as a rock star. Particular attention was given to the big mirror that would focus light onto the light-sensing elements, which was praised as a masterpiece of precision workmanship.

Unfortunately, this mirror did not live up to its image (still another low-flying pun!) Due to a manufacturing error, one edge of it was off by about one-fiftieth of the width of a human hair. In astronomy, that’s enough. Some science could still be done, but the faulty mirror severely compromised the quality of the images, and parts of the mission would have to be canceled.

Somebody should write a book about the valiant and almost superhuman efforts of ground crews in correcting or compensating for problems with spacecraft. On many occasions, missions that seemed to be hopelessly doomed have been resurrected and successfully completed, because the folks on the ground just refused to give up. This was one of those occasions.

Hubble was scheduled to get its first servicing mission in 1993. Rushing to meet this deadline, engineers designed a device to fix the optical problem. The system was called the Corrective Optics Space Telescope Axial Replacement, or COSTAR.

In December of that year, COSTAR went into space. Working in two teams, the astronauts performed a record of five back-to-back spacewalks, during which COSTAR was installed and the Wide Field/Planetary Camera was replaced with an improved unit. In addition, there were routine maintenance jobs to be done, such as putting in new solar arrays and replacing four of the satellite’s gyroscopes.

The fix worked. After that, Hubble started sending back sharper images, and NASA (possibly in an attempt to salvage its damaged image) released reams of them to the press. One of the earliest and most popular was the gorgeous picture of the star-forming region in the Orion nebula, which ended up on countless calendars, posters, screen savers, etc. After that, there were many others: stars like diamond dust set against swirls and streamers of nebular gas, so detailed and delicate that it could have been painted.

Some of us had always known that space was beautiful, but now the whole world knew it.

The pictures are famous now; some of the best ones have been compiled into a gallery at the NASA website, which is certainly worth a look. But as nice as they are, pictures aren’t everything. This was supposed to be a science mission, and while the folks who make calendars, posters and screen savers must have been grateful for the new material, that really wasn’t the point of all this. 20 years on, we can now ask: just what have we learned from Hubble?

In reading over the history of Hubble at the NASA site, a few highlights stood out. Here are a few of them:

1. Observing the evolution of accretion discs around stars. The current theory of planet formation says that it all starts with the accumulation of a cloud of gas. The gas gets denser and denser, especially at its center, which finally gets so compressed that the atoms start to fuse. When that happens, light, heat and other products are emitted, and the result is a star at the center of this condensing gas cloud. Because of the increasing gravity, the rest of the gas begins to spin, just as water spins when it goes down the drain of a bathtub. The spin makes the cloud of gas get flat and disc-shaped, which causes it to be more concentrated. This concentration makes the gas molecules collide with each other and begin to form dust grains, which will eventually clump together to form planets. In observing other stars, astronomers would expect to find discs in various stages of evolution, and Hubble has done that. In January of 2005, NASA scientists announced that Hubble had found several stars with dust discs, and that some of these discs have a flared, thick edge, while others don’t. This shape was expected from computer simulations. The scientists think that the stars with the thick edges are in the early stages, and probably have not formed planets. It is thought that all of the other stars originally had flared edges, too, but the dust that was in them has already formed planets. While this theory of planet formation has been around for some time, this was the first time that “before and after” pictures have been taken of actual stars going through the process.

2. Observing the seasons of Pluto. In February 2010, NASA released pictures of Pluto taken by Hubble. These are our most detailed pictures of that body ever taken, and they show Pluto changing colors over a period of time. During the period of observation (2000 to 2002), Pluto became significantly redder, while the northern hemisphere got brighter. It is thought that the color change is the result of surface ices evaporating over one pole and then refreezing over the other pole, as Pluto starts the next phase of its year, which lasts for 248 Earth years. Just taking these shots was a challenge, since the resolution necessary is comparable to that needed to read the brand name on a soccer ball 40 miles away.

3. Imaging of cross-shaped “comet-like object”. This one has both scientific value and visual appeal. It is a picture of a structure shaped like a cross, with trails swept back by the solar wind. NASA scientists think this is the remnant of a recent collision between two asteroids. The lines of the cross are trails left by the two objects, and the long trails behind the object are particles of debris from the impact. It was an amazing stroke of luck to catch the object right after such an impact, and we may never see another one. The picture is stunning. It’s a safe bet that this one will end up hanging on a few walls, too.

4. First detection of organic molecules on a planet orbiting another star. Last but not least, this one has enormous implications for future space exploration. If nature is going to create life, it has to have the right ingredients. While it is possible to imagine exotic forms of life with bizarre chemistries, the only kinds of life that we know are made from what we call organic molecules. If we can find planets with organic molecules, there is a chance we may be able to find lifeforms there. Until recently this was just theoretical, but in March of 2008, Hubble detected the organic molecule methane in the atmosphere of a Jupiter-size planet in the constellation Vulpecula, some 63 lightyears from here. While this planet is too hot for the kind of chemical reactions that would create life, just finding an organic molecule on another planet is a big step.

The list goes on, and Hubble isn’t done yet. In May of 2009, astronauts made a repair mission to Hubble, refurbishing it for further duty. Now it’s sending back lots of wonderful pictures again, and hopefully will continue to do so for years to come. At 20 years and counting, it is certainly one of the most successful missions in the history of space exploration- and we haven’t seen the last from it yet.

Sources:

“Hubble Space Telescope History” at aerospaceguide.net: aerospaceguide.net/spacehistory/hubble-history.html

“Hubblesite: Hubble Discoveries” at the NASA website: hubblesite.org/hubble_discoveries/

Feature: “Hubble Finds MIssing Link in Planet Formation” at NASA website: nasa.gov/vision/universe/newworlds/0112_missing_link.html

“20 Years of Hubble: Hubble Finds First Organic Molecule on an Exoplanet” at NASA website: nasa.gov/mission_pages/hubble/science/hst_img_20080319.html

“20 Years of Hubble: New Hubble Maps of Pluto Show Surface Changes” at NASA website: nasa.gov/mission_pages/hubble/science/pluto-20100204.html

“20 Years of Hubble: Suspected Asteroid Collision Leaves Odd X-Pattern of Trailing Debris” at NASA website: nasa.gov/mission_pages/hubble/science/asteroid-20100202.html

This is an exciting time.  As we have seen in previous articles, there are a lot of fascinating projects going on right now, with robot probes exploring places in the solar system and beyond.  Places that used to be just names in textbooks are now real places to us, and we are learning more about them all the time.

However, it should never be forgotten that the exploration of the mysterious third planet on which we live can be just as interesting, and of even more vital importance.  To help us understand more, there is now a legion of satellites orbiting Earth to study various aspects of its environment.  Many of these are assessing the consequences of environmental tampering by humans, and finding that those consequences are proceeding at a faster pace than was originally thought.

In assessing the consequences of global warming, one of the indicators that is available to us is the Earth’s ice.  We already know that ice in the polar regions is shrinking to levels unknown in recorded history.  Ships can now sail through places that were completely blocked by ice only a few years ago, but this is only anecdotal evidence, and does not tell us how fast the problem is moving or how far it has already gone.  Before 2000, it was thought that the interiors of the major ice sheets were largely stable.  This was based on data gained by satellite altimetry, but the capability of those satellites to measure change at the margins of ice caps, where most of the change was occurring, was limited by their design. By 2006, new information was emerging which was causing scientists to doubt the stability of the ice caps.  In that year, analysis of radar readings of the Pine Island Glacier in Western Antarctica showed a definite thinning of the ice layer. Data from other satellites, such as ESA’s Envisat, mapped the Earth’s ice and found that annual average Arctic sea ice extent had shrunk by 2.8% per decade since 1978.

But even with that information, we still don’t have the full picture.  To get that, it’s necessary to measure the thickness of the ice.  That’s the only way to get an accurate estimate of the amount of ice that is left, and how quickly it is retreating.

To address this need, CryoSat-2 was designed as part of Earth Explorer, a larger project which addresses key questions regarding the natural processes of our planet, and in some cases, how they are changing in response to the stresses placed on them by human activity.

CryoSat was originally intended to be the first of these probes, not the last.  In one of those terrible disappointments that occasionally happen in space exploration, the first version of CryoSat was lost due to launch failure in October 2005.  The ESA immediately started planning for a relaunch.  Cryosat-2 took four years of preparation, and during that time, the other phases of the Earth Explorer Series proceeded as planned.  While CryoSat was being rebuilt, the GOCE gravity mission and the SMOS water mission were launched successfully, and when CryoSat-2 went up today, it completed the series that it was supposed to start.

Cryosat-2 carries technology to measure changes in two types of ice: the huge sheets covering Greenland and Antarctica, and floating ice in the oceans.  The satellite will travel in a highly inclined polar orbit which will reach 88 degrees latitude north and south, to get maximum coverage of the poles.  Its main instrument is the Synthetic Aperture Interferometer Radar Altimeter (SIRAL).  Radar altimeters used in the past have been designed for use over ocean or land, but SIRAL is the first one to be specifically made for use on ice.

SIRAL has a higher resolution than earlier radar altimeters.  Whereas conventional radar altimeters send out radar pulses that are, on average, 500 microseconds apart, SIRAL send its pulses at intervals of only 50 microseconds.  The onboard data processor can separate the echo into strips which are about 250 m. wide.  Since the interval between bursts is arranged so that the satellite moves forward by 250 m. each time, the strips laid down by successive bursts can be superimposed on each other and averaged to reduce noise.   This is known as the SAR (Synthetic Aperture Radar) mode.

In order to get accurate readings, it is necessary to pinpoint the position of the satellite with great precision.  To accomplish this, CryoSat-2 uses the DORIS (Doppler Orbit and Radio Positioning Integration by Satellite) system.  The satellite’s radio receiver measures the Doppler shift of signals from a network of more than 50 radio transmitters around the globe.  The true accuracy of the reading can only be obtained by processing on the ground, but the raw data provides a usable estimate, good to about half a meter.  The DORIS network has been in use for more than ten years, and has been used for various satellites, including ESA’s Envisat.

This locates the satellite itself, but in addition to this, it is necessary to determine the precise orientation of the baseline of the two antennas that receive the signal.  To obtain this baseline, CryoSat-2 uses the sailor’s old friends, the stars in the sky.  There are three startrackers on the antenna support structure, and each of them takes five pictures per second.  The onboard computer compares the images to a catalogue of star positions.  The orientation of the baseline of the receiving antennas is determined using this positioning data.

Unlike many other Earth-orbiting satellites, CryoSat-2 does not have a sun-synchronous orbit- in other words, it does not orbit in such a way as to receive sunlight all the time.  Instead, the satellite’s path is such that there will be times when Earth is between it and the sun.  This presented some design challenges, as the satellite will regularly be subjected to extreme temperature shifts.  Because of this, it was necessary to insulate the precise instrumentation to maintain optimal operating temperature.

Except for a few valves in the propulsion system, CryoSat-2 has no moving parts at all.  Even the solar panels, rather than being deployable as in most other satellites, are rigidly fixed to the body of the craft, forming the “roof” of the structure.  The lack of moving parts allowed a significant cost savings in the satellite’s manufacture.

Knowledge is our best weapon in the fight against the long-term consequences of global warming.  It is a sad truth that we gained the ability to destroy our world before we learned how to fully assess the damage, so the process went on for years before we realized it.  Now we are in the uncomfortable position of having to measure just how far the process has progressed, and what, if anything, we can do about it.  CryoSat-2 is a new tool for that measurement, and from it, we will gain a new understanding of our planet and its processes.  If we could see the history books of tomorrow, how would they speak of this project, and the other Earth-sensing projects that are going on now?  Will they see this as the beginning of recovery, or just a futile assessment of our hopelessness?  Perhaps these measures will only provide us with a precise gauge of the inevitable end, or perhaps not.  Much environmental damage has already been done, and will not be corrected soon- but the knowledge we gain from CryoSat-2 may help us to lessen the impact, at least.

And it will give us a lot of interesting things to ponder, too.  From it, we may pry a few more secrets from this world on which we have always lived, but which we still do not know very well.  In that sense, this is another fascinating, alien planet to explore, because the things we are learning now are totally new.  It’s all part of our growing knowledge of the mysterious third planet.

Sources:

“Successful Launch for ESA’s CryoSat-2 Ice Satellite” at website of the European Space Agency:  esa.int/esaCP/SEMH5ZZNK7G_index_0.html

“ESA CryoSat: an Earth Explorer” at website of the European Space Agency: esa.int/SPECIALS/Cryosat/SEMHSTOJH4G_0.html

“ESA CryoSat: an Icy Mission” at website of the European Space Agency:  esa.int/SPECIALS/Cryosat/SEMFJ4908BE_0.html

“ESA CryoSat: Earth’s Changing Ice” at website of the European Space Agency:  http://www.esa.int/SPECIALS/Cryosat/SEMQK4908BE_0.html

“ESA CryoSat: Platform” at website of the European Space Agency:  esa.int/SPECIALS/Cryosat/SEMFN4908BE_0.html

“ESA CryoSat: the Instruments” at website of the European Space Agency:  esa.int/SPECIALS/Cryosat/SEMRQ4908BE_0.html

As often happens in the field of space exploration, the idea was way ahead of the reality.  The mission’s unusual name is a salute to Italian astrophysicist Guiseppe “Bepi” Colombo, who originally figured out the course that such a flight should take.  In 1975, Colombo proposed a plan to NASA by which a spacecraft could swing close to Mercury three times by making gravity-assist maneuvers around Venus.  The plan would have worked, but was too ambitious for NASA at the time; it got shelved and forgotten.  Now the years have passed, and things that were once unattainable seem within reach.

Unfortunately, Bepi Colombo died in 1984.  Another sad fact about space exploration is that those who think up the great ideas often don’t live long enough to see them come of age.  The mission that he proposed years ago is going to happen at last, and it will bear his name.

BepiColombo will be launched aboard a Soyuz-Fregat rocket from Kourou, French Guiana.   The date seems to be uncertain; the JAXA website says it’s 2013, but the ESA site says 2014.  (It’s possible that the mission plans were changed in the early stages, as often happens, and that these two postings reflect different versions of the plan.)  BepiColombo’s objectives are to make precise observations of the planet’s magnetic field, magnetosphere, interior and surface.

One of the main questions that it will try to answer is why, of all the planets in the solar system, only Earth and Mercury have active magnetic fields.   Actually, we know why Earth has one, but knowing that just makes Mercury more perplexing.   Earth has an active magnetic field because it has a molten layer surrounding its solid inner core.  The innermost core is compressed into a solid by gravity, but above that, there is a viscous, molten layer called the outer mantle.  The fluid contains iron, and as it moves around the core, the entire planet becomes a giant electrical generator.  The principal is exactly the same as generators here on Earth, in which a rotor moves around a stator, creating an electrical field.  In this case, we see the basic concept expanded to a planetary scale, and the field that results is so strong, it forms lines of magnetic force that stretch around the whole planet.  The important point here is that without the molten outer layer and the solid inner layer moving past each other, you wouldn’t get the magnetic field.  It’s being constantly generated and replenished by that spinning motion inside the planet.

If Earth’s molten outer core were to cool down and become solid- which will happen eventually, in our planet’s old age- the magnetic field would no longer be generated.  Of course, this does not mean that the earth’s magnetic field would suddenly disappear.  We all know that when you place a piece of iron in a magnetic field for a while, it becomes magnetized, too.  If you cut off the magnetism, the iron will still retain some of that energy, but it will be weaker than the original source, and it will fade with time.  If the iron is all mixed up with a bunch of rocks and other stuff, and the mixture is of a very uneven consistency, then the magnetism will fade at an uneven rate.  If there’s more iron in one spot than another, then of course, that spot will hold the magnetism longer.  Eventually you will end up with a glob of iron and rock and stuff which has a very weak, uneven magnetic field around it.  If you had the instruments to measure it, it would be immediately obvious that this was an old, fading field rather than an active one that is being constantly replenished from within.

Let’s leave Mercury for a moment and look at Mars.  This planet has a weak, spotty magnetic field, which tells us that it once had a molten outer core like Earth’s, but that core has now become solid and is no longer generating magnetism.  This is not surprising, because Mars is smaller than Earth, and must have lost the initial heat of its birth faster than Earth has.  Mars is said to have a “fossil” magnetic field.

So here we have the two extremes: Earth with its active field, and poor old Mars with its weak, faded one.  In the old days, when we were looking at Mercury from afar, the popular thought was that it would probably have no magnetic field at all, or if it did, the field would only be a fossil field.   The reasoning was that since Mercury is considerably smaller than either Earth or Mars, it should have long since lost all of the original heat from its formation.  And despite the fact that Mercury is the closest planet to the sun, it still isn’t hot enough to melt rock.  After all, the planet’s surface is still quite solid.  Since the inner region of the planet should have lost all of its original heat, and is insulated by all the rock that lies above it, it must be cooler than the sun-baked surface.  So, if the surface is solid, the core should be, too.  Looking at it logically, you get a picture of a small planet with a relatively cool and very solid interior.

Or so we thought, back in the olden days.  When Mariner 10 made its flyby of Mercury in March of 1974, it revealed what nobody had expected to find: an active magnetic field.  Amazingly, this little planet seems to have a molten portion in its interior, just as Earth does.  Either that, or the current theory about how planetary magnetic fields are generated is completely wrong.  If that’s the case, it means we’ll have to throw away all the textbooks and start over at square one- and since this would be a scandalous waste of paper, we can only hope that it won’t be necessary.  A less revolutionary explanation is that Mercury may have large amounts of radioactive material in its interior, which generates enough heat to melt iron and form a molten mantle- but at the moment, this is pure speculation.

In any case, the planetary scientists certainly want to have a closer look.  The part of BepiColombo’s instrumentation which was contributed by JAXA is the Mercury Magnetospheric Orbiter (MMO) which will observe the planet’s magnetic field with unprecedented accuracy in an effort to better understand its configuration and how it is being created.  It is hoped that the probe can also reveal how Mercury’s magnetosphere differs from Earth’s.  Since these are the only bodies known to have magnetospheres, it is possible that comparing the two will help us understand  something about both of them.

Another job of the MMO is to observe the tenuous exosphere of Mercury.  Rather than a gaseous atmosphere like Earth’s, Mercury is surrounded by a very thin layer of atoms, mainly sodium, that have been blasted off the surface by the fierce solar radiation and the impacts of micrometeorites.  These atoms quickly heat up and escape into space, so Mercury never builds up as much pressure as Earth’s atmosphere has.  This exosphere has never been studied in detail before, and the MMO will observe its structure and the process of formation and escape into space.

The other component of the BepiColombo mission is the Mercury Planetary Orbiter (MPO), contributed by the European Space Agency.  The function of this probe is to study Mercury as a planet: its form, interior, structure, geology, composition and craters.  This will result in a more accurate and detailed map of Mercury than we have ever had before, as well as a better understanding of just what the planet is made of.

One specific question that will be addressed by the MPO is whether there is frozen water at Mercury’s poles.  In the flyby of Mariner 10 back in 1974, the satellite received radar reflections from the polar regions, so we know that there’s something highly reflective there.  Nature doesn’t produce many things that are that reflective; frozen water is the most common.  And it makes sense, because there are areas at Mercury’s poles that are permanently shaded, and probably have been been since the planet was formed.  As strange as it seems, the closest planet to the sun has places that have never felt sunlight, and may be the coldest piece of ground in the solar system.  The MPO will subject these areas to closer scrutiny, looking for ice.

Like some other places in the solar system, Mercury is interesting because it can tell us something about the system’s early times.  On Earth, any substances that we find have been crushed, melted, reformed, eroded and then reformed again, possibly many times over.  There really isn’t much pristine matter from the solar system’s birth for us to study here.   On some of the other bodies in the system, there may be more unchanged matter that can give us a better picture of the original accretion disc which gave birth to all of this.  In particular, if there is ice at the Mercurian poles, it may be a sample of the water vapor that was present in that disc around the sun, which froze in those early times and has remained frozen ever since.  As you can imagine, the planetary scientists are itching to get a peek at it.

The questions are there, just waiting to be answered- and BepiColombo will bring us some of those answers.  By the time it arrives in 2020, we should already have a lot of new information on Mercury from NASA’s MESSENGER probe, which will have been in orbit around the planet for nine years.  BepiColombo will fill in more of the gaps in our knowledge, providing us with our most complete picture yet of the sun’s first planet.    The projected mission is only supposed to last for one Earth year, but there is the possibility of an extension beyond that.

BepiColombo is a big, ambitious mission with huge potential.  It is a remarkable technical achievement, and in the coming years it will bring us some fascinating science about one of the last unexplored bodies in our system.

The fun is just beginning!  As the news comes in, you get always get it here.

Sources:
Mercury Exploration Mission “BepiColombo” at website of Japan Aerospace Exploration Agency:  jaxa.jp/projects/sat/bepi/index_e.html

BepiColombo page at website of the European Space Agency:  sci.esa.int/science-e/www/area/index.cfm?fareaid=30

BepiColombo Overview on the Science and Technology page at website of the European Space Agency:  esa.int/esaSC/120391_index_0_m.html

World Book at NASA- Mercury:  nasa.gov/worldbook/mercury_worldbook.html

Mercury: Closest Planet to the Sun at website of National Geographic:  science.nationalgeographic.com/science/space/solar-system/mercury-article.html

BepiColombo: Mercury Interior at website of the European Space Agency:  sci.esa.int/science-e/www/object/index.cfm?fobjectid=31272

The Northern Lights have been occurring for thousands of years ”“ long before anybody had a scientific explanation for them. Many primitive people regarded the lights as an omen of war or misfortune; some Eskimo groups believed the lights were the spirits of children who had died at birth, or animal spirits dancing. The Algonquin Indians even believed that the lights were reflections of huge fires, constructed by the creator of the earth, Nanahbozho. In medieval Europe, the lights were said to foretell of famine, war or other disaster.

The lights are actually caused by the earth’s magnetic field interacting with solar winds, creating a type of light known as an aurora. As well as emitting heat and light, the sun also emits gas, sometimes known as solar wind. Upon reaching the earth, this gas will collide with the earth’s magnetic field and create energy. The excess energy created by these collisions is given off in the form of light emissions ”“ what we call the northern lights.

One of the fascinating things about seeing the northern lights is that the patterns and colors are constantly changing ”“ no two nights are exactly the same. The most common color is green, although just about any color ”“ red, blue, yellow or purple – can occur in more intense light displays, making the experience even more dramatic. The green color is created by oxygen molecules that are found about 60 miles above the earth; different types of gas particles help to create the other colors. Many people claim that the lights resemble a spectacular sunset or sunrise.

The lights actually occur during the day as well, although it’s virtually impossible to see them. The northern lights do occur year round, but the best time of year to observer them is during the equinoxes ”“ March/April and September/October. They also follow a cycle of about 11 years and scientists have determined they will be at their peak in 2013. At night, the best view of the lights is enjoyed with a clear sky, and no street lighting or other bright lights nearby. In general, if the sky is clear enough to see the Milky Way, your chances of seeing the northern lights are good.

The northern lights occur most frequently in the areas around both the North and South Poles, due to the strong magnetic fields found here. For this reason, the further north you travel, the better your chances of seeing the lights, although they have been seen as far south as Texas and Georgia. In Europe, Iceland and Scandinavia are ideal places to see them; and in North America, the best view is from Alaska and parts of Northern Canada. There are actually southern lights as well ”“ known as aurora australis ”“ although they can only be seen from parts of  Australia, Antarctica and South America.