What Does The Far Side Of The Moon Look Like?

Have we taken any sort of video, or still pictures of the dark side of the moon?
An oblique view of the Crater Daedalus on the lunar farside as seen from the Apollo 11 spacecraft in lunar orbit. Daedalus (formerly referred to as Crater No. 308) is has a diameter of about 50 miles. This is a typical scene showing the rugged terrain on the farside of the moon. Image credit: NASA

An oblique view of the Crater Daedalus on the lunar farside as seen from the Apollo 11 spacecraft in lunar orbit. Daedalus (formerly referred to as Crater No. 308) is has a diameter of about 50 miles. This is a typical scene showing the rugged terrain on the farside of the moon. Image credit: NASA

Originally posted on Forbes!

We absolutely have, and they are super fun! A first point of clarification, though - there’s no “dark side” of the Moon.

There’s a far side which is never visible from our perspective on the Earth, but with the exception of during a full moon, the far side of the moon is at least partially illuminated. Any portion of the side facing us which isn’t lit by the Sun means that a corresponding fraction of the far side is brightly lit. During a New Moon, therefore, when the hemisphere of the moon which faces us is dark, the entire far side of the Moon is illuminated by the Sun. Ultimately, the far side of the moon is bright for exactly the same length of time as the near side!

The lunar farside as seen by the Lunar Reconnaissance Orbiter Camera. The Lunar Reconnaissance Orbiter Camera was designed to acquire data for landing site certification and to conduct polar illumination studies and global mapping. Image credit: NASA/GSFC/Arizona State University

The lunar farside as seen by the Lunar Reconnaissance Orbiter Camera. The Lunar Reconnaissance Orbiter Camera was designed to acquire data for landing site certification and to conduct polar illumination studies and global mapping. Image credit: NASA/GSFC/Arizona State University

Because the far side of the moon is perpetually hidden from us here on Earth, its features are not nearly as familiar to us as the features of the side facing us, visible to anyone who looks up at the sky. On top of that intrinsic lack of familiarity, the far side of the moon is also a very different place than the near side is; it’s almost entirely missing the smooth(ish) dark mare which make up the most obvious landmarks on the near side. The far side instead is almost entirely craters; craters piled within other craters, jumbled on top of each other in a chaotic, rough terrain.

These images are also relatively new to us. We didn’t know how different the far side would be until spacecraft with cameras had been sent to go examine the other half of the Moon. The first images from the far side of the moon came from the USSR spacecraft Luna 3, in 1959. It’s been less than 60 years since those first photos were returned to Earth. By current standards, they’re rather poor images, but they were good enough to tell us that the far side of the Moon was nothing like the near side.

Rugged highland terrain on the farside of the Moon, south of Cantor crater, taken at sunset. Image width is ~3.4 kilometers. Although the pronounced shadows hide the interiors of craters, the high incidence angle exaggerates the surrounding terrain so that subtle surface features are enhanced. Image credit: NASA/GSFC/Arizona State University

Rugged highland terrain on the farside of the Moon, south of Cantor crater, taken at sunset. Image width is ~3.4 kilometers. Although the pronounced shadows hide the interiors of craters, the high incidence angle exaggerates the surrounding terrain so that subtle surface features are enhanced. Image credit: NASA/GSFC/Arizona State University

We got another stack of images of the lunar far side shortly afterwards, during the Apollo era. During the Apollo missions, one of the three crew members stayed in the orbiting capsule which would return all three of them home, while the other two journeyed down to the lunar surface. The astronauts who stayed in these capsules instead got a tour of the far side of the Moon, and took a number of photos of the surface from orbit. One such is at the top of the page, taken by Michael Collins.

Nowadays, we have a lot more spacecraft with very impressive cameras aboard, and they send back very detailed pictures of all sides of the Moon. One of these is NOAA's Deep Space Climate Observatory (DSCOVR) satellite which hosts the Earth Polychromatic Imaging Camera (EPIC) for NASA. DSCOVR orbits the Sun slightly on a smaller orbit than the Earths’, at a stable point called L1. This allows the satellite to stay pointed at the Earth, but also to keep a good perspective. DSCOVR therefore sits about a million miles away from the Earth, many times farther than the orbit of the Moon. Every so often, the Moon will cross in front of the Earth, relative to DSCOVR, and EPIC can grab a series of images (which we can turn into a video) of the lunar far side, fully illuminated by the Sun.

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Why Don't Space Suits Go Rigid When Astronauts Go On Spacewalks?

Why don’t space suits inflate like a Michelin Man when on the Moon or outside the Space Station?
In this photo, Astronaut David A. Wolf, STS-112 mission specialist, anchored to a foot restraint on the Space Station Remote Manipulator System (SSRMS) or Canadarm2, carries the Starboard One (S1) outboard nadir external camera. Image credit: NASA

In this photo, Astronaut David A. Wolf, STS-112 mission specialist, anchored to a foot restraint on the Space Station Remote Manipulator System (SSRMS) or Canadarm2, carries the Starboard One (S1) outboard nadir external camera. Image credit: NASA

Originally posted on Forbes!

They very easily could! If you had a poorly designed space suit or an overly pressurized suit, an astronaut could very easily find themselves immobilized, unable to contort their suit into a useful position. With the inside of a suit set to normal sea level pressure, and the outside of the suit set to the vacuum of space, a fabric suit with no hinges will very quickly stiffen into an inflated posture, and would be very difficult to bend.

In fact, this very situation posed a serious problem for the first spacewalk, conducted by Alexey Leonov, whose suit inflated, and became an obstacle to re-entering the airlock of his spacecraft. With the airlock too small to accommodate a totally puffed-up spacesuit, Leonov had to manually depressurize his suit so that he could bend his arms and legs enough to creep back into the spacecraft. This is not a recommended path to getting around in space; it gave Leonov a very rapid depressurization experience (like “the bends” that divers can experience if they rise from the crushing depths of the ocean too rapidly): hardly good for you and certainly painful.

NASA invited the public to vote on three cover layer designs for the Z-2 prototype suit, the next step in NASA’s advanced suit development program. By using Luminex wire and light-emitting patches, this design puts a new spin on spacewalking standards such as ways to identify crew members. Image credit: NASA

NASA invited the public to vote on three cover layer designs for the Z-2 prototype suit, the next step in NASA’s advanced suit development program. By using Luminex wire and light-emitting patches, this design puts a new spin on spacewalking standards such as ways to identify crew members. Image credit: NASA

There are two solutions that let you avoid inflation of a suit; one is to reduce the pressure inside the suit, and the other is to build your space suit with hinges, so that you never have to compress the air inside the suit by folding it over on itself. Current space suits usually try to do both, which helps makes the process of leaving the home sanctuary of the space station a little easier on our astronauts.

Instead of being pressurized to one atmosphere at sea level, the current iteration of space suits for spacewalks are typically pressurized to only about a third of that. Having a smaller internal pressure means that the suit is less rigidly inflated when “outside”, in space. However, it does mean that the astronaut has to spend some time getting used to this reduction in pressure, and making sure their blood is still getting a safe amount of oxygen.

Once they’re outside, though, even with a smaller internal suit pressure, the astronauts might still struggle to bend the suit. If you look at the sleeves on a long-sleeved shirt, if you bend your arms, a bunch of fabric folds over onto itself at the inside of the elbows. This is usually not an inconvenience to us, but that’s because the air inside our sleeves is the same pressure as the air outside our sleeves. In space, each crinkle in the suit changes the volume of the suit; any change in volume means that the air pressure changes. If you increase the number of folds when you bend your arms, you decrease the amount of room the air has to fill, and the pressure will increase. The solutions here are to either build a huge number of folds into the suit, so that any bending motion won’t change the internal volume, or to make the suit contain a large number of swivel points.

Developed at NASA Ames Research Center in the 1980s, the AX-5 high pressure, zero prebreathe hard suit was developed. It achieved mobility through a constant volume, using a hard metal / composite rigid exoskeleton design. Image credit: NASA

Developed at NASA Ames Research Center in the 1980s, the AX-5 high pressure, zero prebreathe hard suit was developed. It achieved mobility through a constant volume, using a hard metal / composite rigid exoskeleton design. Image credit: NASA

An extreme version of the swivel point approach is the hard-sided prototype suits that NASA developed in the 1980s. This suit was almost 100% hinge, but the principle was that you would never have to bend the suit - the hard-sided spacesuit would simply be able to reshape itself into the needed configuration. Because there’s no bending, the suit could be pressurized to something closer to sea level air pressure, which means getting into and out of it will take less preparation.

The Z-1 is NASA's next generation spacesuit, a prototype of which is pictured at the Johnson Space Center. Image credit: NASA

The Z-1 is NASA's next generation spacesuit, a prototype of which is pictured at the Johnson Space Center. Image credit: NASA

The current space suits, along with the next generation of suits, are mostly made of flexible fabric, but take the “insert all the folds you’ll think you’ll need” approach, with tactically placed folded segments at elbows, knees, and shoulders. These joints, along with the lower air pressure in the suit, allows the astronauts to move with most of the dexterity they’re used to, and perform the repairs, replacements, and other adjustments that the ISS periodically requires! But if you were to just make an airtight suit, with no particular hinges, and pressurize it to the air pressure at sea level, you would absolutely have an inflation problem.

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How Do We Map The Earth’s Gravity?

Can Earth’s center of gravity be located? And if so, to what precision?
Satellite measurements offer scientists a new view of our planet. Warm colors (red, orange, yellow) represent areas with strong gravity. Cool colors (green, blue) represent areas with weak gravity. Image credit: NASA's Goddard Space Flight Center

Satellite measurements offer scientists a new view of our planet. Warm colors (red, orange, yellow) represent areas with strong gravity. Cool colors (green, blue) represent areas with weak gravity. Image credit: NASA's Goddard Space Flight Center

Originally posted on Forbes!

Earth’s center of gravity can be located! We talked a few months ago about measuring the force of gravity surrounding the Moon, and that the way we do this measurement is by having twin satellites, and calculating the difference in gravitational pull on each satellite. As the satellites go over high density regions, the one of them will feel an increased pull before the other, and the distance between the two satellites will change. These tiny changes in the distance between the two satellites allow us to map out the density of the ground below, but it's fundamentally a measure of the strength of the gravitational pull of the ground below the satellites.

We can do the exact same thing for pairs of satellites around the Earth, and we have! The Gravity Recovery and Climate Experiment (GRACE) is a NASA mission to do precisely this. It was a pair of satellites, launched in 2002, which bounced microwaves back and forth between them, very precisely measuring the distance between them, to a sensitivity of about a micron (many times smaller than the width of a human hair.) By additionally communicating with GPS satellites, the GRACE satellites were able to precisely communicate both their absolute positions in orbit around the Earth (to a precision of about a centimeter), and their motions relative to each other. Any deviations in their relative distances should be due to something down below, on Earth.

Artist's rendering of the twin satellites that will compose NASA's Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission. Image credit: NASA/JPL-Caltech

Artist's rendering of the twin satellites that will compose NASA's Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission. Image credit: NASA/JPL-Caltech

ESA has also had one of these earth-measuring satellites, called GOCE (Gravity field and steady-state Ocean Circulation Explorer) which operated between 2009 and 2013. Instead of having two independent satellites, it had two sets of accelerometers at opposite ends of one, long, tubelike satellite, which each measured gravity at their end of the satellite.

Both experiments were able to generate maps of the Earth’s gravitational field strength from their locations in orbit. In practice, these are often reported back as a “geoid”, which is a way of deforming the Earth’s sphere so that any point on its surface would have an equal gravitational strength. Anything built up into a lump outwards indicates that there’s extra mass there, and anything sunken inwards indicates that there’s less mass. GOCE managed to map the gravitational strength of the Earth beneath it to a precision of 10^–5 m/s2.  While we commonly quote the gravitational force as 9.81 m/s^2, this satellite was measuring it out to 0.00001.

ESA's GOCE mission has delivered the most accurate model of the 'geoid' ever produced, which will be used to further our understanding of how Earth works. The colours in the image represent deviations in height (–100 m to +100 m) from an ideal geoid. The blue shades represent low values and the reds/yellows represent high values. Image credit: ESA/HPF/DLR

ESA's GOCE mission has delivered the most accurate model of the 'geoid' ever produced, which will be used to further our understanding of how Earth works. The colours in the image represent deviations in height (–100 m to +100 m) from an ideal geoid. The blue shades represent low values and the reds/yellows represent high values. Image credit: ESA/HPF/DLR

You’ll notice that both of these experiments have another facet to their names - GOCE also says it’s monitoring the ocean circulations, and GRACE is also a climate experiment. That’s because these very precise gravitational measurements can also track the motion of water around our planet. Not just the locations of surface water, or the amount of water in the oceans versus at the poles, but underground water, in reservoirs. Water is a relatively dense material, and so its presence or absence in a certain location will alter the average density of the planet underneath either of these observatories.

GRACE has a follow-up mission, intended for launch this year - GRACE-FO. The FO stands for Follow-On, and is intended to increase the accuracy of the GRACE experiment dramatically, by using laser beams to check the distances between the satellites, instead of microwaves. GRACE-FO will also help us continually monitor our fragile world’s water supplies as the original GRACE satellites age. Not every satellite lasts 15 years, after all.

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Is There Water On The Moon?

A NASA spacecraft explores the moon's permanent shadows. Image credit: NASA's Goddard Space Flight Center

A NASA spacecraft explores the moon's permanent shadows. Image credit: NASA's Goddard Space Flight Center

Originally posted on Forbes!

There is! Water’s existence on the Moon is not an easy thing to arrange, because water evaporates very easily. On our relatively balmy Earth, our evaporating water is mostly caught and suspended in the atmosphere, which in turn is protected from the Sun and other cosmic hazards by the Earth’s magnetic field.

The Moon, having no magnetic field, and also having no atmosphere, has no protection for its water, and no way of catching any of the water which evaporates under the heat of the light from the Sun. This combination of missing ingredients means that we can all reasonably expect that any water on the surface on the Moon would not last long before evaporating. Once the water evaporates and turns into a gas, it can rapidly be stripped away from the Moon, lost to interplanetary space.

The Moon is a jagged and weird place, and so the only shelter the Moon can offer from the Sun’s rays is simply that of shadow. Most of the Moon is illuminated by the Sun at some point in the month -- when the side facing the Earth is dark, it’s the far side that’s bearing the brunt of the Sun’s roasting. But the jaggedness and weirdness of the moon means that there are some very dark shadowy places at the poles of the Moon - craters which are never angled in such a way that the Sun’s light can reach their depths. And, in the same way that the snow patch underneath a parked car doesn’t melt very rapidly, any water ice in the depths of one of these permanently shadowed craters could also stay put for much longer than any exposed water ice would ever manage.

NASA's Moon Mineralogy Mapper, an instrument on the Indian Space Research Organization's Chandrayaan-1 mission, took this image of Earth's moon. Blue shows the signature of water, green shows the brightness of the surface as measured by reflected infrared radiation from the sun and red shows an iron-bearing mineral called pyroxene. Image credit: ISRO/NASA/JPL-Caltech/Brown Univ./USGS

NASA's Moon Mineralogy Mapper, an instrument on the Indian Space Research Organization's Chandrayaan-1 mission, took this image of Earth's moon. Blue shows the signature of water, green shows the brightness of the surface as measured by reflected infrared radiation from the sun and red shows an iron-bearing mineral called pyroxene. Image credit: ISRO/NASA/JPL-Caltech/Brown Univ./USGS

However, it wasn’t until 2008, when the Indian satellite Chandrayaan-1 was placed into orbit around the Moon that the presence of water in these deep craters was 100% confirmed. In 2009, multiple instruments onboard Chandrayaan-1 recorded signatures of significant amounts of water at the poles of the Moon.  Since those first reports, other satellites (including the LCROSS lunar impactor) have confirmed the initial results, and the Lunar Reconaissance Orbiter continues to map out the depths of these craters at the poles of the Moon even today.

How did that water get there? That’s much harder to determine. But it’s estimated that the water arrived through several pathways. The easiest, given the cratered nature of the moon, is that it arrived with an impacting object, like a comet or water-laden asteroid. It’s hard to say if that would donate enough water, so there may yet be other ways that water arrived on the surface of the Moon, or perhaps is formed through interactions with the solar wind.

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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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