Second chances in space missions are exceedingly rare. When something goes wrong it often means either a total loss of the mission or a significantly reduced outlook for what the mission can accomplish. Primarily this comes down to the tight engineering challenges that space missions face, with multiple redundant systems only able to cope with so much. Still every so often they happen and sometimes a new mission is born out one that might have been a failure. Such is the story of JAXA’s Akatsuki craft, one that has been lying in wait for the last 5 years waiting for its chance to fulfill its mission.
Akatsuki launched 5 years ago aboard JAXA’s H-IIA rocket. It was to be JAXA’s second interplanetary probe after their first, Nozomi, failed to reached its intended destination over a decade prior. The insertion burn was confirmed to have started on schedule, however after the communications blackout period where the probe was behind Venus it failed to reestablish communications at the expected time. It was found drifting away from Venus in safe mode, indicating that it had undergone some form of failure. In this state it was operating in a very low bandwidth mode and so it took some time to diagnose what had happened. As it turned out the main engine had fired for only 3 minutes before failing, not enough to put it in the required orbit.
However it was enough to put Akatsuki on a leading orbit with Venus, one that would eventually bring it back around to meet the planet some time in the future. It was then decided that JAXA would attempt recovery of the craft into a new orbit around Venus, a highly elliptical orbit with a period of almost 2 weeks (the originally intended orbital period was approximately 30 hours). Investigation into the craft’s damaged sustained during the first initial burn showed that the main engine was unusable and so the insertion burn would be performed by its attitude thrusters. JAXA had a lot of time to plan this as the next scheduled rendezvous would not happen for another 5 years.
Following some initial maneuvers back in July and September Akatsuki began its orbital insertion burn on the 7th of December. The small attitude thrusters, designed to keep the spacecraft oriented, fired for 20 straight minutes far beyond what they were originally designed for. They did their job however and 2 days later JAXA announced that they had successfully entered orbit around Venus, albeit in the far more elliptical orbit than they originally planned.
The extended duration in space has likely taken its toll on Akatsuki and so JAXA is currently undertaking a detailed investigation of its current status. 3 of its 6 cameras have shown to be fully functioning with the remainder scheduled to be brought online very soon. Scientific experiments using Akatsuki’s instruments won’t begin until sometime next year however as an orbital correction maneuver is planned to reduce Akatsuki’s orbit slightly. However JAXA is confident that the majority of their science objectives can be met, an amazing boon to both their team and the wider scientific community.
It’s incredibly heartening to see JAXA successfully recover the Akatsuki craft after such a monumental setback. The research conducted using data from the Akatsuki craft will give us insights into why Venus is such a strange beast, rotating slowly in opposite direction to every other planet in our solar system. Whilst I’d never wish failure upon anyone I know the lessons learnt from this experience will bolster JAXA’s future missions and, hopefully, their next one won’t suffer a similar fate.
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 I think of a tidally locked planet, like say Mercury, the only image that comes to mind is one that is barren of all life. You see for tidally locked systems the face of the smaller body is always pointing towards the larger one, like our Moon is towards Earth. For planets and suns this means that the surface of the tidally locked planet would typically turn into an inferno with the other side becoming a frigid wasteland, both devoid of any kind of life. However new research shows that these planets might not be the lifeless rocks we once thought them to be and, in fact, they could be far more Earthlike than we previously thought.
Scientists have long theorized that planets of this nature could potentially harbour a habitable band around their terminator, a tenuous strip that exists between the freezing depths of the cold side and the furnace of the hot side. Such a planet wouldn’t have the day/night cycles that we’re accustomed to however and it would be likely that any life that evolved there would have adapted to the permanent daylight. There’d also be some pretty extreme winds to contend with as well due to the massive differences in temperature although how severe they were would be heavily dependent on the thickness of the atmosphere. Still it’s possible that that little band could harbor all sorts of life, despite the conditions that bookended its environment.
However there’s another theory that states that these kinds of planets might not be the one sided hotbeds that we initially thought them to be. Instead of being fully tidally locked with their parent star planets like this might actually still rotate thanks to the heavy winds that would whip across their surface. These winds would push against the planets surface, giving it enough rotation to overcome the tidal locking caused by the parent star’s gravity. There’s actually an example of this within our own solar system: Venus which by all rights should be tidally locked to our Sun. However it’s not although it’s extremely long days and retrograde rotation (it spins the opposite way to every other planet) hints at the fact that its rotation is caused by forces that a different to that from every other planet.
Counterintuitively it seems that Venus’ extremely thick atmosphere might be working against it in this regard as the modelling done shows that planets with thinner atmospheres would actually experience a higher rotational rate. This means that an Earthlike planet that should be tidally locked would likely not be and the resulting motion would be enough to make the majority of the planet habitable. In turn this would mean that many of the supposedly tidally locked planets we’ve discovered could actually turn out to be habitable candidates.
Whilst these are just beautiful models for now they can hopefully drive the requirements for future craft and observatories here on Earth that will be able to look for the signatures of these kinds of planets. Considering that our detection methods are currently skewed towards detecting planets that are close to their parent stars this will mean a much greater hit rate for habitable candidates, providing a wealth of data to validate against. Whether we’ll be able to get some direct observations of such planets within the next century or more is a question we won’t likely have an answer to soon, but hopefully one day we will.
Venus is probably the most peculiar planet that we have in our solar system. If you were observing it from far away you’d probably think that it was a twin of Earth, and for the most part you’d be right, but we know that it’s nothing like the place we call home. It’s atmosphere is a testament to the devastation that can be wrought by global warming with the surface temperature exceeding 400 degrees. Venus is also the only planet that spins in the opposite (retrograde) direction to every other planet, a mystery that still remains unsolved. Still for all we know about our celestial sister there’s always more to be learned and that’s where the Venus Express comes in.
Launched back in 2005 the Venus Express mission took the platform developed for the Mars Express mission and tweaked it for observational use around Venus. The Venus Express’ primary mission was the long term observation of Venus’ atmosphere as well as some limited study of its surface (a rather difficult task considering Venu’s dense atmosphere). It arrived at Venus back in early 2006 and has been sending data back ever since with its primary mission being extended several times since then. However the on board fuel resources are beginning to run low so the scientists controlling the craft proposed a daring idea: do a controlled deep dive into the atmosphere to gather even more detailed information about Venus’ atmosphere.
Typically the Venus Express orbits around 250KM above Venus’ surface, a pretty typical height for observational activities. The proposed dive however had the craft diving down to below 150KM, an incredibly low altitude for any craft to attempt. To put it in perspective the “boundary of space” (referred to as the Karman line) is about 100KM above Earth’s surface, putting this craft not too far off that boundary. Considering that Venus’ atmosphere is far more dense than Earth’s the risks you run by diving down that low are increased dramatically as the drag you’ll experience at that height will be far greater. Still, even with all those risks, the proposed dive went ahead last week.
The amazing thing about it? The craft survived.
The dive brought the craft down to a staggering 130KM above Venus’ surface during which it saw some drastic changes in its operating environment. The atmospheric density increased a thousandfold between the 160KM and 130KM, significantly increasing the drag on the spacecraft. This in turn led to the solar panels experiencing heating over 100 degrees, enough to boil water on them. It’s spent about a month at various low altitudes before the mission team brought it back up out of the cloudy depths, where its orbit will now slowly degrade over time before it re-enters the atmosphere one last time.
It’s stuff like this that gets me excited about space and the science we can do in it. I mean we’ve got an almost decade old craft orbiting another planet and we purposefully plunged it down, just in the hopes that we’d get some better data. Not only did it manage to do that but it came back out the other side, still ready and raring to go. If that isn’t a testament to our talents in engineering and orbital mechanics prowess then I don’t know what is.
It’s almost scary how similar Earth and Venus are in some respects. We’re roughly the same size, with Earth edging Venus out by 300KMs in diameter, and consequently roughly the same mass as well. The similarities end when you start looking further however with Venus being the hottest planet in our solar system due to its runaway greenhouse effect, it’s atmosphere a choking combination of carbon dioxide, nitrogen and sulphur. If there was ever a warning about the devastating potential about greenhouse gases it is our celestial sister Venus, but in that chaos lies an abundance of scientific data that could help us better understand ourselves and, hopefully, avoid the same fate.
Studying Venus’ atmosphere isn’t an easy task however as those extreme conditions have meant that the longest our probes have managed to survive down there is a couple hours. We can still do a lot of good work with satellites and spectral analysis but there’s really no substitute for actually being in the atmosphere for an extended period of time. Strangely enough whilst Venus’ atmosphere might be one of the most unforgiving in our solar system its composition, made up primarily of heavy than air elements, provides an unique opportunity that an atmospheric study craft could take advantage of. A concept craft that does just this is called the Venus Atmospheric Maneuverable Platform (VAMP) by Northrop Grumman.
The VAMP is part airship, part traditional aircraft which would spend the majority of its life high in Venus’ atmosphere. To do this the VAMP craft is extremely light, on the order of 500kgs, but it has a wingspan that exceeds that of a Boeing 737. The craft itself would be inflatable, allowing VAMP to cruise at altitudes between 55KM and 70KM above Venus’ surface. It can do this because of the incredible density of Venus’ atmosphere which makes even regular breathable air from Earth a powerful lifting gas. The only limit to its lifespan in the Venusian atmosphere would be its power source and since it could take advantage of the freely available sun a platform like VAMP could run for an incredibly long time.
The concept is actually a rework of another one that was designed to fly through the atmosphere of Saturn’s moon Titan, a mission many have wanted to undertake since the Huygens probe landed there a decade ago. The challenges of flying an aircraft there are far greater than that of Venus, primarily due to the much thinner atmosphere and huge drop in solar radiation to take advantage of. It would still be doable of course, however the mission profile you’d have to go with would have to be much less ambitious and the time frames much shorter. Still it surprises me that the concept didn’t go the other way around as putting balloons in Venus’ atmosphere has always been a concept that many wanted to explore.
Northrop Grumman appears to be quite serious about the VAMP project as they outlined many objectives they wanted to achieve for it back in 2013. I can’t seem to find much more on it unfortunately which means it’s likely still in the concept phase, hoping for a mission profile to come along that suits it. Considering how many incredible envelope pushing missions we’ve had of late I don’t think something like VAMP is too far out of left field, especially considering that it’s based on already proven technologies. Still it doesn’t seem like it will be too long before we have a plane soaring through another world’s atmosphere, another science fiction dream becoming a reality.
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.
Whilst the vastness of space can not be underestimated, as I wrote about yesterday, there is still a lot for us to see out there. If we are to take a blind stab in the dark as to how many stars there are out there we end up with numbers in the ranges of 1024 or 1 000 000 000 000 000 000 000 000 (1 septillion) give or take a few hundred billion. Now consider how many of those stars would have planets or solar systems around them. This is where we start to imagine what that big number means for life in the universe.
Before we delve into the wonderful world of potential alien species I want to take you back to 1992. Before this day we could only speculate about solar systems outside our own. For us it would appear obvious that other stars out there had planet systems like our own considering the sheer number of potential stars out there. Even if the chance of generating a system like ours was a 1 in 1 trillion chance there would still be a million of them around. However we’d never actually proved that there were any planets outside our solar system, that was until Aleksander Wolszczan and Dale Frail discovered PSR B1257+12B (romantic I know) the first ever planet to be detected outside our solar system. It was a brilliant discovery at the time as up until then claiming the discovery of a planet was at the very edge of our capability. Several years later with improvements in technology and detection methods many more were discovered, with 358 being totalled to date.
Out of these 74 of them belong to multiple star systems, or approximately 20% of the observations so far. It’s a long stretch to say that 20% of all stars are hosts to multiple planet systems but we could assume 50% (to be generous) or greater are capable of hosting 1 or more planets. This leaves us with approximately 1 trillion potential candidates for planet formation in the universe with 20% of those having multiple chances. If this is sounding familiar to you then you already know I’m describing the drake equation, which attempts to predict the number of civilisations that we might be able to make contact with. So far the most common result of that equation is around 10, meaning just within our own galaxy there are 10 other species we would be capable of making contact with. Slight tweaks of the variables either way swing it wildly, and shows just how little we know for certain when it comes to estimating things like this.
The other side of this is the Fermi paradox which stipulates that despite the evidence to the contrary we haven’t actually managed to find signs of life through either contact or observation. Even our current list of exoplanets doesn’t have one on it that would be capable of supporting life as we know it (although that’s due to selection bias of the methods more than anything else). As the old saying goes absence of evidence is not evidence of absence, so we’re stuck at this point until we find some new data that points us in the right direction.
More interestingly is the potential for life within our own solar system. Take a look at Mars and Venus, two very similar planets to Earth that have very different fates. Mars on the one hand was too small to hold onto whatever atmosphere it had at the beginning and the lack of a magnetic field left it to fall prey to the solar winds. However studies have shown that Mars was once home to vast oceans and as such would have had most of the ingredients for supporting life. Since we haven’t found any signs of life yet it’s possible that there was something missing, and as such life never progressed. It is also possible that life died out as the planet’s protective barriers were withered away, but we’ll need to find something like a fossil before that’s even a possible past for Mars.
Venus on the other hand is something of a warning as to what can happen to a planet when it suffers from a runaway greenhouse effect. As far as we can tell Venus was very similar to Earth when they both first formed however strong volcanic activity has turned the planet into a hothouse, smothering it in clouds of sulphur and carbon dioxide. This has lead to a surface temperature above 400 degrees putting the chances of life there squarely at 0. This effect also stops us from making extended observations on Venus, so the possibility of it supporting life in the past is hard even to estimate. Curiously as well Venus has what we call a retrograde rotation, meaning that it spins in the opposite direction to every other planet in the solar system. As to why this happened we’re still not sure (and it seems the astrology cranks love harping on about it) although the best guess seems to be a combination of tidal locking forces and solar heating of Venus’ atmosphere.
Taking all of this into consideration you really get a feel for how unique and fragile life is. However, as our planet has shown, the conditions are right millions of different forms of life can prosper. I can not wait for the day when we discover another planet capable of supporting life and I hope that it’s not too far away.