MESSENGER was a great example of how NASA’s reputation for solid engineering can extend the life of their spacecraft far beyond anyone’s expectations. Originally slated for a one year mission once it reached it’s destination (a 7 year long journey in itself) MESSENGER continued to operate around Mercury for another 3 years past its original mission date, providing all sorts of great data on the diminutive planet that hugs our sun. However after being in orbit for so long its fuel reserves ran empty leaving it unable to maintain its orbit. Then last week MESSENGER crash landed on Mercury’s surface putting an end to the 10 year long mission. However before that happened MESSENGER sent back some interesting data around Mercury’s past.
As MESSENGER’s orbit deteriorated it creeped ever closer to the surface of Mercury allowing it to take measurements that it couldn’t do previously due to concerns about the spacecraft not being able to recover from such a close approach. During this time, when MESSENGER was orbiting at a mere 15KMs (just a hair above the max flight ceiling of a modern jetliner) it was able to use its magnetometer to detect the magnetic field emanating from the rocks on Mercury’s surface. These fields showed that the magnetic field that surrounds Mercury is incredibly ancient, dating back almost 4 billion years (right around the creation of our solar system). This is interesting for a variety of reasons but most of all because of how similar Mercury’s magnetic field is to ours.
Of all the planets in our solar system only Earth and Mars have a sustained magnetic field that comes from an internal dynamo of undulating molten metals. Whilst the gas giants also generate magnetic fields they come from a far more exotic form of matter (metallic hydrogen) and our other rocky planets, Venus and Mars, have cores that have long since solidified, killing any significant field that might have once been present. Mercury’s field is much weaker than Earth’s, on the order of only 1% or so, but it’s still enough to produce a magnetosphere that deflects the solar wind. Knowing how Mercury’s field evolved and changed over time will give us insights not only into our own magnetic field but of those planets in our solar system who have long since lost theirs.
There’s likely a bunch more revelations to come from the data that MESSENGER gathered over all those years it spent orbiting our tiny celestial sister but discoveries like this, ones that could only be made in the mission’s death throes, feel like they have a special kind of significance. Whilst it might not be the stuff that makes headlines around the world it’s the kind of incremental discovery that gives us insight into the inner workings of planets and their creation, something we will most definitely need to understand as we venture further into space.
Whenever the idea of establishing a colony off-world comes to mind the first place many think of is Mars. Primarily this is due to Mars being the most similar of all the other planets to ours, having an atmosphere and land features that look very similar to some of our own. However that’s where the likeness ends as its lack of magnetic field has meant that its atmosphere has been stripped bar to a thin layer of carbon dioxide, taking all of the surface water along with it. Thus whilst it would seem like the best candidate for humans to establish themselves elsewhere in this solar system there are other potential sites that have distinct advantages over what Mars can provide.
One surprisingly good candidate for a potential human colony is Mercury. Now initially this would seem like a pretty bad idea as its surface temperatures regularly exceed several hundred degrees celsius and the only atmosphere to speak of is a tenuous layer is mostly made up of solar wind and vaporized surface material. However it’s close proximity to the sun gives it access to abundant solar power, orders of magnitude more than what is available on the surface of Mars. Considering that power is probably one of the biggest limiting factors for a colony and the size it can grow this advantage could prove invaluable, so long as the initial challenges could be overcome.
Probably the biggest thing that Mercury has going against it is the time it would take to get a mission there. Whilst we’ve got craft today capable of covering the distance in under 40 days or so its tight orbit around our sun makes it incredibly difficult to get into orbit with it. It’s not so much that it’s hard to do, more that the time typically required to transit to there with an approach that will get you into orbit takes on the order of years, not days. This would mean the development of systems to support humans for a sustained period in space which would open up other alternative locations for a human colony.
Interestingly such systems could be used to establish a colony on Venus, although not the type you’d think of. Whilst Venus’ surface is a hellish place where it rains metal it would be quite possible to create cloud cities that float around an area that’s much more hospitable to humans. Indeed the pressure at 50KM above the surface is the same as Earths and thanks to the dense, mostly carbon dioxide atmosphere a lifting gas that’s simply breathing air has a lifting power of 50 times that of helium on earth. The protections required then are far less strenuous than those required to get to Mercury initially and the dangers posed by the atmosphere are far less severe than that of a harsh vacuum.
Past these planets though are options start to get limited as whilst many moons of the gas giants of the outer solar system have an abundance of things like water or other useful materials they’re typically quite harsh environments, either being flooded with ionizing radiation or lacking any kind of atmosphere without the benefit of having high amounts of light to take advantage of. They’re essentially equivalent to space itself in that regard and whilst I love the idea of large human colonies in space there’s really no substitute for colonizing another planet.
For what its worth we’re likely going to see a Mars colony within our lifetimes, one that will likely be limited to a few one way pioneers or entrepreneurs looking to take advantage of the first new frontier in a century. The other options, whilst being only slightly more fantastical than that of a Mars colony, aren’t likely to happen any time soon as there needs to be much more ground broken in engineering terms before they become viable. Regardless of where it happens a human colony off our planet is fast becoming a necessity if we want to ensure the human race doesn’t have a single point of failure in our own planet.
Mercury is a strange little beast of a planet. It’s the closest planet to our sun and manages to whip around it just under 88 days. Its “days” are 59 earth days long and whilst it’s not tidally locked to our parent star (like the moon is to us, always showing the same face to the earth) it is in a 3:2 spin-orbit resonance. This has led to some interesting phenomena when we’ve sent probes to image it as the only probe to ever visit it, Mariner 10, only managed to image 45% of the planet’s surface on it’s 2 encounter trip with the tortured little planet. That all changed a few years ago when MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) made its first approach to Mercury in January 2008 and sent back images of the as of yet unseen side of the planet. Ever since then MESSENGER has been on a long trajectory that will eventually bring it into orbit with Mercury and it will begin it’s year long mission of observations.
It just so happens that that day is today.
MESSENGER has been in space for an extremely long time, almost 7 years. You might be wondering why it has taken this craft so long to reach Mercury and the answer requires that you understand a little about orbital mechanics. You see as a heavenly body, in this case a satellite, moves closer to another body it will tend to speed up. This is known as the conservation of angular momentum and it’s the same principle that governs the increase in speed when you bring your arms in closer whilst you’re spinning. Thus for a satellite that’s launched from Earth to be able to orbit Mercury it has to shed all that extra speed so it can match up to it, otherwise it would just whiz right past it. Since doing this with a rocket is rather expensive (the fuel required would be phenomenal) NASA instead opts to shed velocity by a complicated set of maneuvers between planets, each of which removes a portion of the satellite’s velocity. This is cheap fuel wise but means the space craft will have to endure many years in space before it reaches its destination.
As I write this MESSENGER is making its final preparations to insert itself into an orbit around Mercury. MESSENGER hopes to demystify the diminutive planet by providing hi-resolution imaging of the planet (there’s still 5% we haven’t seen yet), doing chemical analysis to determine the planet’s makeup and attempting to figure out why Mercury has a magnetic field. Probably the most interesting part of MESSENGER will be the last part as our current theories on planet formation point to Mercury being much like our moon with a solid core and no magnetic field to speak of. The presence of one there suggests that part of Mercury’s core is still molten and raises a number of questions over how planets and natural satellites like our moon form. It will also be the first ever artificial satellite of Mercury, something that still eludes many of the other planets in our solar system.
This is the kind of science that NASA really excels at, the stuff that just hasn’t been done before. It’s really amazing to see NASA flex their engineering muscle, designing systems that survive in the most unforgiving environment we know for decades and still function as expected. The next year will be filled with all kinds of awesome discoveries about our tortured little cousin Mercury and I for one can’t wait to see how the analysis of its magnetic field changes the way we model planet formations in the future.
I’d love to say that ever since I was a little boy I would lie awake at night staring at the stars and wanting to go up there, but I would be wrong. As a kid I barely knew about the wonders of space and the kinds of technology that have taken us up there. It was only after I turned 21 did I start getting interested in space, only just on a year ago that I decided I would be visiting outer space in my lifetime, by any means possible.
Anyone who knows me will tell you how passionate I am about space and how humanity must become a spacefaring civilisation. As a child born many years after our glory days of landing on the moon I’ve only been able to witness humanities various robotic accomplishments (which are great and many) and the wonder that is the International Space Station. For the next 10 years though I will be on tenterhooks as we, hopefully, plan to make our glorious return to the moon and beyond. That gives me something to look forward to, no matter what else happens along the way.
The reason I’m so passionate about space is that whenever I start talking about it most people will only know about the Apollo missions, the Shuttle and possibly the Mars rovers. Few know about the bravery of the Mercury and Gemini Astronauts, or the amazing inginuity of the Mir space station. It seems that ever since the end of the Apollo missions, humanity has found space to be boring and kids don’t grow up wanting to be Astronauts anymore.
I’ve come into the world of Aeronautics late in life, and I sometimes lie awake at night wondering what kind of life I would be leading now if I realised that my passion lied in outer space. Who knows, I might be living in the United States right now eagerly awaiting my first shuttle flight (although, history has shown youngsters like myself aren’t usually considered for another few years). What I do appreciate though is that the world in its current state is on the verge of a critical mass in terms of space for the masses. Soon we will have sub-orbital flights (a la the Mercury Program) and when that all goes well, we’ll be seeing orbital flights not too long afterwards.
I guess I just long for the days when you asked kids what they wanted to be when they grow up many of them would say Astronaut. The reason I miss those days so much is because it meant that Space exploration was so mainstream that even the children knew about it and were excited to participate in it. We’re really still in the infancy of Space flight (regular flight has really only become mainstream in the past decade) so it is with our children that the future of humanity in Space will lie.
To get you a little inspired, here are some pictures from the recent shuttle mission STS-126, which upgraded the International Space Station in order for it to handle double the crew starting next year.