Could We Protect Mars-Bound Astronauts With A Magnetic Bubble?

Could a synthetic magnetic bubble, like a mini-magnetosphere, protect a crewed mission to Mars from cosmic radiation, and would the energy cost be prohibitively high?
A NASA mission reveals how gases in Mars' upper atmosphere are stripped away by the sun's solar wind. Image credit: NASA's Scientific Visualization Studio and the MAVEN Science Team

A NASA mission reveals how gases in Mars' upper atmosphere are stripped away by the sun's solar wind. Image credit: NASA's Scientific Visualization Studio and the MAVEN Science Team

Originally posted on Forbes!

As much as some folks are keen on sending people to Mars as soon as possible, it’s become obvious that protecting any astronauts from an unsafe level of radiation before they even get to Mars is going to be a tricky business.

There are two main problems for astronauts leaving our home planet; one is cosmic rays, which are usually turbo-speed protons from outside of our solar system. Some cosmic rays are blocked by our Earth's magnetosphere, and the remainder are usually stopped by our atmosphere. The other problem comes direct from the Sun itself; the Sun also flings electrons and protons in our direction in the solar wind. The solar wind is mostly stopped by our magnetosphere, but if you’re going out a bit further, we won’t have that protection.

The solar wind is a stream of particles, mainly protons and electrons, flowing from the sun's atmosphere at a speed of about 1 million mph. Image credit: NASA's Scientific Visualization Studio and the MAVEN Science Team

The solar wind is a stream of particles, mainly protons and electrons, flowing from the sun's atmosphere at a speed of about 1 million mph. Image credit: NASA's Scientific Visualization Studio and the MAVEN Science Team

The solar wind is usually relatively easy to protect yourself from; with a slightly thicker wall than the bare minimum on your spacecraft, you can usually protect your crewmembers from a solar wind related battering. However, cosmic rays are harder to stop. The protons which make up cosmic rays typically have more energy to them, so shielding has to be more robust. The second problem with cosmic rays is that sometimes they’re more than just a proton; they can be an entire helium nucleus (two protons, and two neutrons), making them a projectile that’s both very high speed and four times the mass of a solar wind particle. These enormous cosmic rays can break apart, at an atomic level, the material they crash into, filling the interior of your spacecraft with radiation, which is not great for anyone trying to live in there.

Once a spacecraft leaves the Earth’s protective bubble, not only does the cosmic ray dose increase dramatically, but you’ve also got a much less protected place to deal with the solar wind. And if the Sun decides to unleash a solar flare in your direction, you’ve got an awful lot of protons coming your way from the Sun, in addition to the galaxy in general pelting you with helium nuclei.

Enlil model run of the July 23, 2012 CME and events leading up to it. This view is a 'top-down' view in the plane of Earth's orbit. Image credit: NASA's Scientific Visualization Studio, the Space Weather Research Center (SWRC), the Community-Coordinated Modeling Center (CCMC), Enlil and Dusan Odstrcil (GMU), Leila Mays (CUA) and Janet Luhmann (UCB) and NASA's Scientific Visualization Studio.

Enlil model run of the July 23, 2012 CME and events leading up to it. This view is a 'top-down' view in the plane of Earth's orbit. Image credit: NASA's Scientific Visualization Studio, the Space Weather Research Center (SWRC), the Community-Coordinated Modeling Center (CCMC), Enlil and Dusan Odstrcil (GMU), Leila Mays (CUA) and Janet Luhmann (UCB) and NASA's Scientific Visualization Studio.

Unprotected, a solar flare can rapidly give you radiation sickness, which makes you tired and also makes you vomit. Fortunately for all involved, most spacecraft have thick enough walls that the crew should be protected from solar flares, but it’s generally considered good practice to reduce all possible risks. On the other hand, cosmic rays are not so easily stopped.

Because cosmic rays are fundamentally a charged particle, using a miniature magnetosphere surrounding the spacecraft would be an effective way of keeping them away from both your crew and the walls of the spacecraft; if this could be built into a spacecraft, you wouldn’t need to bulk up the outer surfaces of the craft for radiation protection. However, actually doing so is a bit beyond us at the moment. There have been a number of proposed magnet configurations developed, and a recent simulation of three different styles indicated that the magnetic shielding could, in fact, reduce the overall radiation dose an astronaut would receive. This is not a given, because to create such a magnetic field, you need to add extra stuff to your spacecraft; the more mass you have, the more stuff Galactic cosmic rays can bash into, filling your craft with extra radiation. However, these portable magnetospheres are only just in the design phase --the next big steps will be building them, making them lighter, easier to power and making sure they work they way we hoped they would. At this point, all we can really say is that it should be possible. We'll have to wait and see if it's also practical.

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Have we already contaminated Mars?

Have we not already contaminated Mars by landing and roving, (regarding reluctance to examining water found)?
This self-portrait of NASA's Mars rover Curiosity combines dozens of exposures taken by the rover's Mars Hand Lens Imager (MAHLI) during the 177th Martian day, or sol, of Curiosity's work on Mars (Feb. 3, 2013), plus three exposures taken during Sol 270 (May 10, 2013) to update the appearance of part of the ground beside the rover. Image credit: NASA/JPL-Caltech/MSSS  

This self-portrait of NASA's Mars rover Curiosity combines dozens of exposures taken by the rover's Mars Hand Lens Imager (MAHLI) during the 177th Martian day, or sol, of Curiosity's work on Mars (Feb. 3, 2013), plus three exposures taken during Sol 270 (May 10, 2013) to update the appearance of part of the ground beside the rover. Image credit: NASA/JPL-Caltech/MSSS
 

Originally posted at Forbes!

Contamination of other worlds is a major source of concern, particularly when we’re going someplace that might be habitable for some form of life. All spacecraft (and this includes satellites, telescopes, and rovers) have all of their pieces go through some pretty serious decontamination before launch, and most are assembled in a very high test clean room. (The last time I was near a clean room of this caliber, we weren’t allowed in the corridor that eventually led to the clean room, to try and keep airborne particles to a minimum).

Part of this clean assembly is for the good of the craft itself. Discovering that somehow, dust settled on the mirror of your brand new telescope would be a nightmare scenario; this means that your telescope is seriously underperforming, to the detriment of all the science that it might have been able to do. And you certainly don’t want grit making its way into the moving parts, which could jam the operation of those parts. If the part that needs to move is critical to the success of the mission (say, for instance, it’s your communications antenna), a stuck part could cripple the entire mission. So keeping everything as clean as possible gives the craft itself the best possible chance at operating the way it was intended.

If your spacecraft has a gas chromatograph or a mass spectrometer on it, both of which are instruments designed to sample the molecular properties of a gas, then you have to be extra careful. If you have such a sensitive metric of the chemical composition of air or vaporized soil, any kind of contamination left from Earth on the tray you’re using to hold the gas or dust will contaminate your measurement, and you’ll wind up measuring the contaminant instead of what you really want it to be sampling (Mars, for instance). This has actually been an issue in the past; the Viking landers on Mars made this kind of measurement of some of the soil and found some unusual chemicals in the soil in 1976. Unfortunately for the soil measurement, it was found that you could get this reading either by having Mars be doing some interesting chemistry, or if there was still some residual cleanser on the soil tray.

With some later measurements by the Phoenix lander in 2008, it’s possible that the ‘interesting chemistry’ interpretation is actually the correct one, but until some more measurements are made on the exact isotopes of the atoms involved in the reading, it’ll be hard to rule out the cleanser contamination explanation. Curiosity, on the other hand, seems to have found genuine complex molecules from Mars air and vaporized rock, but the scientists working on the team could only say this after determining that the results of the experiment on different rocks were sufficiently different to rule out contamination. (If you thought the signal you were getting was from a single contaminant on your tray, it would produce a similar signal no matter which rocks you were inspecting.)

Landers so far have been sitting in places that are pretty dry and reasonably flat; the flat part is just because it gives us the best possible chance at actually landing without smashing our spacecraft on an unexpected ledge. The dry tends to go along with the flat; by and large our best observations of material flowing on Mars has been along steep slopes, where it is too dangerous to land. Avoiding those places for the purposes of avoiding contaminating any water reservoirs is done out of an abundance of caution. It’s hard to guarantee that we don’t have any cleanser products left on our rovers, in spite of our best efforts to send as clean a craft as possible. And if there is some form of extreme life out there on Mars, we’d like to not kill it accidentally.


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Is there gold on Mars?

Is there gold on Mars? Could there be gold, agates, or geodes?
Color mosaic of Olympus Mons volcano on Mars from the Viking 1 Orbiter. The mosaic was created using images from orbit 735 taken 22 June 1978. Olympus Mons is about 600 km in diameter and the summit caldera is 24 km above the surrounding plains. Image credit:  NASA/JPL

Color mosaic of Olympus Mons volcano on Mars from the Viking 1 Orbiter. The mosaic was created using images from orbit 735 taken 22 June 1978. Olympus Mons is about 600 km in diameter and the summit caldera is 24 km above the surrounding plains. Image credit: NASA/JPL

Originally posted at Forbes!

It’s certainly plausible! Why? On Earth, each of these things has something in common, that Mars also has: volcanoes.

Gold, like all elements in the periodic table heavier than iron, is formed exclusively when very large stars explode at the end of their lifetimes. The entire Earth’s reservoir of gold is the collected remains of these explosions, created well before our solar system formed. All the gold present on our planet was present in the cloud of dust and gas that eventually collapsed into our solar system.

The early solar system spent a reasonably long time in a “molten protoplanet” phase, where the objects which would eventually become planets had yet to form a solid crust. Most of the metals collected in the core of the planets; this stage was the origin of the nickel-iron core of our planet. (I happen to like the nickel-iron core, since its motions are also responsible for our protective magnetosphere.) Any gold present while this settling process was going on would also have sunk towards the center. Clearly we still manage to find gold on the surface of our planet, so we haven’t lost all of the gold to the fiery depths of our planet.

Our planet is geologically rather active, and and upwellings of heat from our planet’s core find outlets in our systems of volcanoes. The lava that pours (or sometimes explodes) out of a volcano can come from deep within the mantle of the Earth, and so materials that sank out of reach, beneath our crust, can be redeposited on the surface. In this process, dissolved gold can be pulled out of the molten rock and left on the surface for us to discover. (We can also get some additional gold at the surface from impacts from asteroids, but at least on Earth, it seems that volcanic regions are better places to find gold.)

Mars has a set of volcanoes on its surface that contains the largest volcano in the solar system, Olympus Mons. These volcanos resemble the large shield volcanoes on earth (the islands of Hawaii, for instance) so it seems reasonable to suggest that many of the processes that we can see happening on Earth near our volcanoes might also have been present in the ancient, volcanically active Mars. This redepositing of gold on the surface or near the surface may well have also happened on Mars.

Volcanic Region, Mars Elysium Volcanic Region View, By Mars Global Surveyor's Camera (Note Bright Clouds). Image credit: NASA.

Volcanic Region, Mars Elysium Volcanic Region View, By Mars Global Surveyor's Camera (Note Bright Clouds). Image credit: NASA.

What about geodes? Geodes are hollowed out bits of rock, with crystals growing on the inside. The fundamental requirement is to have the hollow present, so that the crystals can grow inside of it. Volcanoes can come to the rescue here as well. The smooth-flowing type of lava frequently creates little bubbles; sometimes these bubbles pop, but sometimes they harden in place. If the bubble survives, over time, water may be able to seep inside, depositing minerals, which can form crystals. We know now that Mars had plenty of water at one point, so this process may also have been possible on Mars.

Agate? Agate also has a volcanic origin. Agate forms when material full of silica (the main ingredient in white sand, and glass) slowly fills or partially fills an irregular hole, perhaps formed by a gas bubble in lava. As the material fills in the hole, it creates the bands you see in some agate, like a tree growing produces bands as it grows.

The problem with finding these things directly is that they’re most likely to be found near the volcanoes. In an abundance of caution, we tend not to try and land things on the volcanoes, as the ground can be very complicated – you can go from “reasonably flat” to “you fell off a cliff” a little faster than we might like when we’re handing a several billion dollar machine. It has proven difficult enough to get any kind of machine to the surface of Mars in the first place, so making it extra dangerous has not been at the top of anyone’s priority list. Olympus Mons has a nearly 10 kilometre high cliff surrounding it, which would make it a particularly difficult climb, even if we managed to land something near that volcano. (This particular problem seems to be unique to Olympus Mons – the smaller volcanos don’t seem to have the same kind of cliffs.)

image

However, we’ve already found a number of interesting minerals on Mars where we have landed rovers! Opportunity found a huge streak of gypsum sticking out of the surface of Mars, and also found hematite ‘blueberries’ – a sign of a wetter past on Mars. Even more minerals have been detected from orbit! But until we can crack some more of the problems with more closely exploring the more volcanic regions of Mars, the presence of gold, agates and geodes on Mars will remain simply plausible!

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Why do we only see one side of the moon?

Lunar libration.  Image credit : wikimedia user  Tomruen .

Lunar libration. Image credit: wikimedia user Tomruen.

The simple answer (and one that you’ve probably heard before) is that we only see one side of the moon because the moon rotates around the Earth at the exact same speed as it rotates around its own axis, so that the same side of the moon is constantly facing the surface of the earth.  This means that one full ‘day’ of the moon (meaning the length of time it takes for the moon to rotate around itself once) is about 4 weeks long.  If the moon didn’t rotate at all, we would see all of its sides; the only way for us to see such a constant face of the moon is if it’s also rotating. There’s a great visualization of this below.

Tidal locking results in the Moon rotating about its axis in about the same time it takes to orbit the Earth. Except for libration effects, this results in it keeping the same face turned towards the Earth, as seen in the figure on the left. (The Moon is shown in polar view, and is not drawn to scale.) If the Moon didn't spin at all, then it would alternately show its near and far sides to the Earth while moving around our planet in orbit, as shown in the figure on the right.  Image credit : Wikimedia user  Stigmatella aurantiaca

Tidal locking results in the Moon rotating about its axis in about the same time it takes to orbit the Earth. Except for libration effects, this results in it keeping the same face turned towards the Earth, as seen in the figure on the left. (The Moon is shown in polar view, and is not drawn to scale.) If the Moon didn't spin at all, then it would alternately show its near and far sides to the Earth while moving around our planet in orbit, as shown in the figure on the right. Image credit: Wikimedia user Stigmatella aurantiaca

If you watch the way the moon spins (or doesn’t), you can see that only the left side has a consistent side facing the surface of our planet (which, we must note, is not even a little bit to scale here).

However, the underlying reason why the moon rotates at this exact speed, forcing us to only see a single side of it, is because the moon has been tidally locked to the earth.  Tidal locking is a stable configuration, and relatively easy to get to, given enough time, so many of our solar system’s moons are found to be tidally locked, including the dwarf planet Pluto and its largest moon Charon, which are both tidally locked to each other.

The “lock” part of this name refers to the way that an object - like the Moon - is apparently fixed in position, with one side always facing the other object.  Any object which is found to be tidally locked will always have one side of itself facing the surface of the planet it’s orbiting.  The amount of time it takes to orbit around the planet will vary from object to object (Phobos, one of the moons of Mars, is tidally locked and orbits Mars every 8 hours - way faster than our Moon), but as long as the object is tidally locked, the rotation will match the length of time it takes to orbit.

However, it’s the “tidal” part of the tidal locking that gives us the real key to why tidal locking happens at all.

We’re most familiar with tides as the effect of our oceans rising and falling due to the position of the moon.  The Moon’s gravity pulls on the earth, and the water on the surface of the Earth closest to the moon responds to that pull by elongating towards the moon. The water on other parts of the earth feels the Moon’s gravitational pull as weaker, with the water on the opposite side of the earth feeling the weakest pull. However, these tidal forces also have another effect - they resist rotation.

The Moon was almost certainly not tidally locked when it first formed - at that time, it would have rotated at a faster speed, which meant that had any observer been on the early Earth, they could have seen all sides of the moon as it spun.  However, the gravitational pull from the Earth - which like the tides due to the Moon, pulls on the side of the Moon closest to the earth more than the far side, resisted this faster rotation. This resistance due to the gravitational pull of the Earth gradually slowed down the faster spin of the Moon until the Moon was no longer rotating faster than it was orbiting.  Once the Moon’s rotation had slowed so much that a single face was always facing the surface of the Earth, it had officially been tidally locked, and has stayed in this configuration ever since.

The Moon also has the same influence on the Earth, but since the Moon is so much less massive than the Earth, this resistance to rotation takes a much longer time to impact the Earth's spin.  However, it’s still a measurable effect! The Moon is slowing down the rotation of the Earth by about 15 microseconds every year, gradually lengthening our days.


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Does life exist in other planets?

We can’t think of a single good reason why it shouldn’t, if the conditions are right!

The hardest part is getting the right conditions. On Earth, the biggest requirement for life is water. Our planet is very good at growing things in every possible location, so long as it’s near or in liquid water. Life arose extremely quickly after the formation of the earth, which seems to indicate that if once the Earth had a surface with liquid water on it, there were not a lot of other stumbling blocks to overcome before life could spring forth.

Having liquid water usually means that the planet has to be in a relatively narrow distance window away from its star, and have a surface upon which the water can rest. Effectively, we need rocky planets at exactly the right distance from the sun such that all the water doesn’t freeze solid or evaporate away. Outside of that distance band in a solar system which allows for liquid water, there are precious few opportunities for liquid water to exist, except in unusual cases like Enceladus, a moon of Saturn, and Europa, a moon of Jupiter. Both of these moons are thought to have an ocean of liquid water under their icy surfaces. These small moons can maintain liquid water because the tidal forces from the massive planets they orbit are constantly stretching the rock at the cores of the moons. This stretching heats up the rock, and that heating provides the energy required to maintain liquid water, even though these moons are far too distant from the sun to keep liquid water on their surfaces. As a result, planetary scientists are very excited about the prospect of being able to find life on Europa and Enceladus, but in order to go check, we’ll have to send a craft to those moons to look directly.

Also within our solar system, we are currently looking for evidence that life once existed on Mars. The information coming back from our Mars rovers tells us that Mars was once warmer and wetter than it is now, which means that it should have been a good place for life, back when it was able to hold liquid water. However, since Mars has become very cold over the years, we don’t expect to find evidence of life currently thriving there.

Looking for planets outside our solar system becomes much more difficult than looking within it; for starters, it’s much more difficult to find the planets to start with. We then need to filter out only the ones that fall within this magic range of distances from their star where liquid water can exist. The technology to find rocky planets in the liquid water zone has only recently been developed. These planets are extremely hard to detect, and push the boundaries of the sensitivity of our telescopes. The Kepler satellite has begun to push into this realm of extrasolar planets, and the massive amount of data it took before the end of its mission is still being analyzed. It seems, from the data that’s been studied so far, that about 20% of all stars like our sun have a planet around it like the Earth - a rocky planet near enough to the star to have liquid water.

Proving that liquid water does in fact exist on those planets is more difficult still - you have to detect the signature of water in the atmosphere of a planet that is light years away. Proving the existence of life will be an even more difficult task, but once we begin to find lots of planets with liquid water on their surfaces, the odds are pretty good that one of them will contain life of some form. It will be much easier to search for life within our own solar system, since we can actually go to these places and see what’s there directly.

No matter where it might be - the search is on.

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