Electric Solar Wind Sail Could Dramatically Reduce Costs of Missions to Mars

Posted Yesterday

According to Janhunen et. al. (2015), the Electric Solar Wind Sail (or E-sail) – a novel propellantless technology capable of “riding” the solar winds – could reduce the cost of navigating the Solar System outside our planet’s magnetosphere to virtually zero.

An artist’s rendering of the Estonian nanosatellite ESTCube-1, which was the first satellite to test the electric “sail”. Image credit: Taavi Torim via Wikipedia.org, CC BY-SA 3.0.

The “sail” is actually an electric field created between charged tethers, arranged centrifugally around the host ship and kept in a high positive potential by an onboard electron gun, that deflect solar wind protons and extract momentum from them. It was invented in 2006 by Pekka Janhunen at the Finnish Meteorological Institute (FMI) in Helsinki, Finland.
This new technology could help turn the idea of asteroid mining into reality – after a suitable water-bearing asteroid is detected, a mining unit could be sent to extract its water by heating it up and collecting the resulting vapour into a cool container. Once the container is full, it would be separated from the “sail” and sent to the orbit of Earth of Mars, where it would be split into hydrogen and oxygen, and turned into a liquid (LH2/LOX). This fuel could then be used to fill the tanks of manned vehicles travelling between the two planets.
Due to the exponential nature of the rocket equation, intermediate tankings reduce the launch mass dramatically. The asteroid-mined water could also be used as radiation shielding of the manned compartment, thereby reducing the launch mass even further.
In addition, with cheap propellant fuel available in Mars orbit, the onboard crew would have the option of an all-propulsive landing, which might potentially eliminate the issues related to the massive and extremely expensive heat shields, and allow for a more precise determination of landing area.
Researchers at the FMI, who were behind the study, think this arrangement – called the Electric Solar Wind Sail Facilitated Manned Mars Initiative (EMMI) – could enable a fundamentally new and economically sustainable approach to manned Mars flights. According to the authors, the “recurrent cost of continuous bi-directional traffic between Earth and Mars might ultimately approach the recurrent cost of running the International Space Station”.
The paper was accepted for publication on March 27 and published on April 3 in the scientific journal Acta Astronautica.
Sources: article abstract, en.ilmatieteenlaitos.fi, sciencedaily.com.

Second Dragon, fruit flies and fresh coffee for Samantha

Posted Today

ESA astronaut Samantha Cristoforetti is nearing the end of her six-month Futura mission but her action-packed stay on the International Space Station is showing no signs of slowing down.

Dragon-6 cargo ferry captured and about to be berthed with the International Space Station on 17 April 2015. ESA astronaut Samantha Cristoforetti controlled the 16 m-long robot arm to grab the spacecraft and pull it to the Station with NASA astronaut Terry Virts providing support. The spacecraft brought fresh supplies and experiments to the weightless research laboratory. Samantha has been performing experiments as diverse as studying fruit flies, investigating small particles in liquids, looking at microscopic worms and growing plants. Copyright ESA/NASA

Last Friday saw the arrival of the second Dragon cargo ferry for Samantha. She controlled the 16 m-long robot arm to grab the spacecraft and pull it to the Space Station with NASA astronaut Terry Virts providing support.
Earlier this year, the Station was visited by a Dragon ferry with Samantha supporting NASA’s Butch Wilmore for the grappling and berthing.
The spacecraft has brought fresh supplies and experiments to the weightless research laboratory. Samantha has been performing experiments as diverse as studying fruit flies, investigating small particles in liquids, looking at microscopic worms and growing plants.

Caenorhabditis elegans is a transparent nematode worm about 1 mm in length. It lives in temperate soil but research shows that it adapts very well to space conditions. Copyright Creative Commons ShareAlike license–B. Goldstein

Science zoo

Fruit flies are a model organism for scientists and are studied extensively – they live for around a week and share many genes with humans. This experiment will chart gene changes over generations of fruit flies in space in relation to diseases.
Samantha has been looking at colloids – small particles suspended in liquids, found in milk and paint for example – for a NASA experiment to understand how they behave without gravity’s interference. This research ties in with ESA’s colloid experiments.
Another common traveller on the Station and an often-studied animal for biologists is the Caenorhabditis elegans worm. Previous research has shown that the worm adapts and even thrives in weightlessness, implying that muscles might age less in space.

ESA astronaut Samantha Cristoforetti working with ESA’s Biolab facility on the International Space Station for the Triplelux experiment. This experiment uses ESA’s Biolab facility in the Columbus laboratory on the Station. Living in space is harmful to living beings – radiation takes its toll on a cellular level, while weightlessness seems to impair immune systems. Copyright ESA/NASA

Samantha looked after the worms and stored generations for analysis in this Japanese-led experiment, as did ESA astronaut André Kuipers on his 2004 mission. This time, however, researchers are looking at changes in DNA over four generations.

Samantha has also been tending to plants for the Aniso Tubule study that is looking at their stems and how they grow in weightlessness compared to Earth. This research will help to grow food crops in space, which would be necessary for longer missions. The research has implications for crops on Earth because plants spend a lot of energy growing stalks. This energy could be diverted to increase production if we knew more about how the mechanisms work.
The latest Dragon spacecraft delivered the second part of ESA’s Triplelux experiment that is investigating the immune system of organisms on a cellular level. Samantha kicked off the Triplelux-B experiment earlier this year by recording how immune cells from the common blue mussel react to an infection. Samantha will continue the experiment now that a second set of samples from a rat’s immune system has arrived.

ESA astronaut Samantha Cristoforetti working with ESA’s Kubik centrifuge on the International Space Station for the Triplelux experiment. Copyright ESA/NASA

Time for coffee

These experiments are just some examples from the Station – read more about her work in Samantha’s logbook. Aside from her 40-hour-plus work week, she finds the time to take astounding pictures of our planet.
A special item on this week’s Dragon is the ‘ISSpresso’ machine that should offer a fresh brew of coffee for the Italian astronaut and her five crewmates. Spending months on the Station cut off from the world can be difficult, but a fresh cup of coffee can work wonders. Future capsules will extend the menu to include tea and soup.

ESA astronaut Samantha Cristoforetti points at the Dargon spacecraft she just grappled on 17 April 2015 with the 16m-long International Space Station robotic arm. A special item on the Dragon spacecraft was the ‘ISSpresso’ machine that should offer a fresh brew of coffee for the Italian astronaut and her five crewmates. Spending months on the Station cut off from the world can be difficult, but a fresh cup of coffee can work wonders. Future capsules will extend the menu to include tea and soup. Samantha published this image with the text: “There’s coffee in that nebula… ehm, I mean… in that Dragon.” Copyright ESA/NASA

Source: ESA

NASA’s NExSS Coalition to Lead Search for Life on Distant Worlds

Posted Today

NASA is bringing together experts spanning a variety of scientific fields for an unprecedented initiative dedicated to the search for life on planets outside our solar system.

The search for life beyond our solar system requires unprecedented cooperation across scientific disciplines. NASA’s NExSS collaboration includes those who study Earth as a life-bearing planet (lower right), those researching the diversity of solar system planets (left), and those on the new frontier, discovering worlds orbiting other stars in the galaxy (upper right). Credits: NASA

The Nexus for Exoplanet System Science, or “NExSS”, hopes to better understand the various components of an exoplanet, as well as how the planet stars and neighbor planets interact to support life.
“This interdisciplinary endeavor connects top research teams and provides a synthesized approach in the search for planets with the greatest potential for signs of life,” says Jim Green, NASA’s Director of Planetary Science. “The hunt for exoplanets is not only a priority for astronomers, it’s of keen interest to planetary and climate scientists as well.”
The study of exoplanets – planets around other stars – is a relatively new field. The discovery of the first exoplanet around a star like our sun was made in 1995. Since the launch of NASA’s Kepler space telescope six years ago, more than 1,000 exoplanets have been found, with thousands of additional candidates waiting to be confirmed. Scientists are developing ways to confirm the habitability of these worlds and search for biosignatures, or signs of life.
The key to this effort is understanding how biology interacts with the atmosphere, geology, oceans, and interior of a planet, and how these interactions are affected by the host star. This “system science” approach will help scientists better understand how to look for life on exoplanets.
NExSS will tap into the collective expertise from each of the science communities supported by NASA’s Science Mission Directorate:

• Earth scientists develop a systems science approach by studying our home planet.
• Planetary scientists apply systems science to a wide variety of worlds within our solar system.
• Heliophysicists add another layer to this systems science approach, looking in detail at how the Sun interacts with orbiting planets.
• Astrophysicists provide data on the exoplanets and host stars for the application of this systems science framework.

NExSS will bring together these prominent research communities in an unprecedented collaboration, to share their perspectives, research results, and approaches in the pursuit of one of humanity’s deepest questions: Are we alone?
The team will help classify the diversity of worlds being discovered, understand the potential habitability of these worlds, and develop tools and technologies needed in the search for life beyond Earth.
Dr. Paul Hertz, Director of the Astrophysics Division at NASA notes, “NExSS scientists will not only apply a systems science approach to existing exoplanet data, their work will provide a foundation for interpreting observations of exoplanets from future exoplanet missions such as TESS, JWST, and WFIRST.” The Transiting Exoplanet Survey Satellite (TESS) is working toward a 2017 launch, with the James Webb Space Telescope (JWST) scheduled for launch in 2018. The Wide-field Infrared Survey Telescope is currently being studied by NASA for a launch in the 2020’s.
NExSS will be led by Natalie Batalha of NASA’s Ames Research Center, Dawn Gelino with NExScI, the NASA Exoplanet Science Institute, and Anthony del Genio of NASA’s Goddard Institute for Space Studies. The NExSS project will also include team members from 10 different universities and two research institutes. These teams were selected from proposals submitted across NASA’s Science Mission Directorate.
The Berkeley/Stanford University team is led by James Graham. This “Exoplanets Unveiled” group will focus on this question: “What are the properties of exoplanetary systems, particularly as they relate to their formation, evolution, and potential to harbor life?”
Daniel Apai leads the “Earths in Other Solar Systems” team from the University of Arizona. The EOS team will combine astronomical observations of exoplanets and forming planetary systems with powerful computer simulations and cutting-edge microscopic studies of meteorites from the early solar system to understand how Earth-like planets form and how biocritical ingredients  — C, H, N, O-containing molecules — are delivered to these worlds.
The Arizona State University team will take a similar approach. Led by Steven Desch, this research group will place planetary habitability in a chemical context, with the goal of producing a “periodic table of planets”. Additionally, the outputs from this team will be critical inputs to other teams modeling the atmospheres of other worlds.
Researchers from Hampton University will be exploring the sources and sinks for volatiles on habitable worlds. The “Living, Breathing Planet Team,” led by William B. Moore, will study how the loss of hydrogen and other atmospheric compounds to space has profoundly changed the chemistry and surface conditions of planets in the solar system and beyond. This research will help determine the past and present habitability of Mars and even Venus, and will form the basis for identifying habitable and eventually living planets around other stars.
The team centered at NASA’s Goddard Institute for Space Studies will investigate habitability on a more local scale. Led by Tony Del Genio, it will examine the habitability of solar system rocky planets through time, and will use that foundation to inform the detection and characterization of habitable exoplanets in the future.
The NASA Astrobiology Institute’s Virtual Planetary Laboratory, based at the University of Washington, was founded in 2001 and is a heritage team of the NExSS network. This research group, led by Dr. Victoria Meadows, will combine expertise from Earth observations, Earth system science, planetary science, and astronomy to explore factors likely to affect the habitability of exoplanets, as well as the remote detectability of global signs of habitability and life.
Five additional teams were chosen from the Planetary Science Division portion of the Exoplanets Research Program (ExRP).  Each brings a unique combination of expertise to understand the fundamental origins of exoplanetary systems, through laboratory, observational, and modeling studies.
A group led by Neal Turner at NASA’s Jet Propulsion Laboratory, California Institute of Technology, will work to understand why so many exoplanets orbit close to their stars. Were they born where we find them, or did they form farther out and spiral inward? The team will investigate how the gas and dust close to young stars interact with planets, using computer modeling to go beyond what can be imaged with today’s telescopes on the ground and in space.
A team at the University of Wyoming, headed by Hannah Jang-Condell, will explore the evolution of planet formation, modeling disks around young stars that are in the process of forming their planets. Of particular interest are “transitional” disks, which are protostellar disks that appear to have inner holes or regions partially cleared of gas and dust. These inner holes may be caused in part by planets inside or near the holes.
A Penn State University team, led by Eric Ford, will strive to further understand planetary formation by investigating the bulk properties of small transiting planets and implications for their formation.
A second Penn State group, with Jason Wright as principal investigator, will study the atmospheres of giant planets that are transiting hot Jupiters with a novel, high-precision technique called diffuser-assisted photometry. This research aims to enable more detailed characterization of the temperatures, pressures, composition, and variability of exoplanet atmospheres.
The University of Maryland and NASA’s Goddard Space Flight Center team, with Wade Henning at the helm, will study tidal dynamics and orbital evolution of terrestrial class exoplanets. This effort will explore how intense tidal heating, such as the temporary creation of magma oceans, can actually save Earth-sized planets from being ejected during the orbital chaos of early solar systems.
Another University of Maryland project, led by Drake Deming, will leverage a statistical analysis of Kepler data to extract the maximum amount of information concerning the atmospheres of Kepler’s planets.
The group led by Hiroshi Imanaka from the SETI Institute will be conducting laboratory investigation of plausible photochemical haze particles in hot, exoplanetary atmospheres.
The Yale University team, headed by Debra Fischer, will design new spectrometers with the stability to reach Earth-detecting precision for nearby stars. The team will also make improvements to Planet Hunters, www.planethunters.org, a web interface that allows citizen scientists to search for transiting planets in the NASA Kepler public archive data. Citizen scientists have found more than 100 planets not previously detected; many of these planets are in the habitable zones of host stars.
A group led by Adam Jensen at the University of Nebraska-Kearney will explore the existence and evolution of exospheres around exoplanets, the outer, ‘unbound’ portion of a planet’s atmosphere. This team previously made the first visible light detection of hydrogen absorption from an exoplanet’s exosphere, indicating a source of hot, excited hydrogen around the planet. The existence of such hydrogen can potentially tell us about the long-term evolution of a planet’s atmosphere, including the effects and interactions of stellar winds and planetary magnetic fields.
From the University of California, Santa Cruz, Jonathan Fortney’s team will investigate how novel statistical methods can be used to extract information from light which is emitted and reflected by planetary atmospheres, in order to understand their atmospheric temperatures and the abundance of molecules.
Source: NASA

The Hard-won Triumph of the Apollo 13 Mission – 45 Years Later

Posted Yesterday

When their spaceship was severely damaged 200,000 miles from Earth – 45 years ago this week, it was like a bad dream from which the Apollo 13 crew could not wake.

Astronauts Fred Haise (left), Jack Swigert and James Lovell pose with the Apollo 13 patch and spacecraft models the day before launch. Image Credit: NASA

Moments after they finished a TV broadcast late on April 13, 1970, a spark ignited one of the oxygen tanks on the Apollo 13 spacecraft. The resulting explosion plunged an entire nation into an anxious three-and-a-half day drama.
The blast obliterated one of three fuel cells and an oxygen tank. Oxygen jetted into space from the command module’s remaining tank.
“Houston, we’ve had a problem here,” astronaut Jack Swigert told mission control in Houston at what was then NASA’s Manned Spacecraft Center (now Johnson Space Center).
“We’ve had a main B bus undervolt,” Mission Commander James Lovell said. One of the command module’s two main electrical circuits had experienced a drop in power.

From their key positions in this control center at Goddard, the Manned Space Flight Network operations director and staff controlled Apollo mission communications activities throughout a far-flung worldwide complex of stations. Image Credit: NASA’s Goddard Space Flight Center

The Manned Space Flight Network at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, made Swigert and Lovell’s reports possible. The network’s tracking stations linked the spacecraft to Earth, where its signals were transmitted through Goddard. Nearly three million circuit miles of communication channels in the NASA Communication Network conveyed the messages received at Goddard to the Mission Control Center in Houston.
Less than two hours after Swigert’s message was transmitted to Houston, mission control pronounced the command module mortally wounded. With only 15 minutes of power left, astronauts Swigert, Jim Lovell and Fred Haise escaped to the “life boat” of the lunar module.
President Richard Nixon learned of the crisis shortly after the explosion, and hemet with Goddard Center Director John F. Clark the following day for an update. William C. Schneider, director of NASA’s Skylab program, briefed the president on the status of the rescue mission in Goddard’s Manned Space Flight Network control room, through which communications to and from Apollo 13 passed.

Then-Goddard Center Director John Clark greets President Richard Nixon, who visited the center for an Apollo 13 briefing on April 14, 1970. At right is Henry Thompson, deputy director of manned flight support at Goddard. Image Credit: NASA’s Goddard Space Flight Center

The nation watched for the latest updates from their television sets, transfixed, as the rescue mission unfolded.
The crew spent three-and-a-half grueling days in the lunar module. They rationed food and water, which mission designers had only intended to last two men a day and a half, not three men three days. Carbon dioxide reached dangerous levels in the lunar module before the team managed to convert square filters from the command module to fit in the round openings on the lunar module. When the crew shut the instruments off to conserve power, the inside temperature reached an icy 38 F.
But reorienting the lunar module to a return-to-Earth trajectory from a lunar landing course proved to be one of the most difficult and important obstacles to hurdle.
Navigation and targeting functions were unavailable. Debris from the explosion made it impossible for the crew to navigate by the stars using the on-board sextant. In a nail-biting maneuver, the astronauts improvised by using the limb of Earth, or the horizon where Earth meets the atmosphere, as a reference point. They were then able to perform a controlled fuel burn to shorten the time ’til splashdown on Earth.

Then-NASA Administrator Thomas Paine (center), together with staff members from NASA Headquarters and the Manned Spacecraft Center, applaud the successful splashdown of the Apollo 13 mission. The splashdown occurred at 12:07 p.m., April 17, 1970, in the south Pacific Ocean. Image Credit: NASA

Flight Director Gerald Griffin in Houston later recalled of the alignment maneuver, “Some years later I went back to the log and looked up that mission. My writing was almost illegible, I was so damned nervous. And I remember the exhilaration running through me: My God, that’s the last hurdle – if we can do that, I know we can make it. It was funny because only the people involved knew how important it was to have that platform properly aligned.”
On April 17, 1970, the crew splashed down in the Pacific Ocean near Samoa.
The performance of Goddard’s Manned Space Flight Network contributed significantly to the safe return of the astronauts, said Dale Call, then-MSFN network director. He said the network performed better then than on any previous Apollo mission.
Houston’s flight operations director commended MSFN operators for their critical help with the mission.
Throughout the crisis, the network remained consistent and reliable in relaying communications to and from Apollo 13 despite the tracking difficulties imposed by the failure of the command module. As engineers on the ground hurriedly created workarounds for each challenge that arose, such as the carbon dioxide issue, they could only be communicated to the crew via the network.
Although the mission was not able to achieve its scientific goals, NASA’s rescue mission was an agency triumph.
“With astronauts Lovell, Haise and Swigert safely back on Earth, a surpassing human drama that gripped the world for three-and-a-half days at last has a happy ending,” President Richard Nixon said following the astronauts’ return. “Their safe return is a tribute to their own courage and also to the ingenuity and resourcefulness of those on the ground who helped transform potential tragedy into a heart-stopping rescue.”

Comet Comes to Life in Amazing Rosetta Spacecraft Photo Montage

by Elizabeth Howell, Space.com Contributor   |   April 14, 2015 02:03pm ET

The heat is on for the Comet 67P/ Churyumov-Gerasimenko as it sails ever closer to the sun, with the European Rosetta spacecraft snapping a stunning set of photos that the buzzing activity of the icy wanderer.
A new montage of comet photos by Rosetta shows gas and dust erupting from Comet 67P as the icy object continues its approach to perihelion, its closest approach to the sun, later this year in August. Already the sun's warmth is making frozen ices evaporate into gas, which carry dust out with it. This creates an envelope of gas surrounding the comet, called a coma.
The Rosetta image series, which the European Space Agency unveiled Monday (April 13), shows the comet's activity between Jan. 31 (top left) and March 25 (bottom right). At the time, Comet 67P was between 226 million and 186 million miles (363 million and 300 million kilometers) from the sun. [Video: Watch Rosetta's Super-Close Comet Encounter]

"As the comet continues to move closer to the sun, the warming continues and activity rises, and pressure from the solar wind causes some of the materials to stream out into long tails, one made of gas, the other of dust," the ESA officials wrote in an image description.
In August, Comet 67P will make its closest approach to the sun as it passes between the orbits of Earth and Mars. At that time, the comet will be about 115 million miles (185 million km) from the sun.
"The comet's coma will eventually span tens of thousands of kilometers, while the tails may extend hundreds of thousands of kilometers, and both will be visible through large telescopes on Earth."
The Rosetta spacecraft has been watching over the comet since arriving in August 2014, keeping an eye out now from a few tens of kilometers above the surface. In past months, it got as close as six kilometers (3.7 miles). It's the first time a spacecraft has spent an extended amount of time with a comet.
In November, Rosetta released a lander called Philae that successfully touched down on the surface, but far off target in a shady spot. Philae fell silent when its solar-powered batteries drained a few dozen hours after landing. Rosetta has tried listening for Philae a few times in recent weeks, but with no success.

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Our sun came late to the Milky Way's star-birth party

Date:

April 9, 2015

Source:

Space Telescope Science Institute (STScI)

Summary:

Astronomers compiled a story of our Milky Way's growth by studying galaxies similar in mass to our galaxy, found in deep surveys of the universe. Stretching back more than 10 billion years, the census contains nearly 2,000 snapshots of Milky Way-like galaxies.

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This artist's illustration depicts a view of the night sky from a hypothetical planet within the youthful Milky Way galaxy 10 billion years ago. ...

Credit: Image NASA, ESA, and Z. Levay (STScI)

[Click to enlarge image]

In one of the most comprehensive multi-observatory galaxy surveys yet, astronomers find that galaxies like our Milky Way underwent a stellar "baby boom," churning out stars at a prodigious rate, about 30 times faster than today.

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Our Sun, however, is a late "boomer." The Milky Way's star-birthing frenzy peaked 10 billion years ago, but our Sun was late for the party, not forming until roughly 5 billion years ago. By that time the star formation rate in our galaxy had plunged to a trickle.
Missing the party, however, may not have been so bad. The Sun's late appearance may actually have fostered the growth of our solar system's planets. Elements heavier than hydrogen and helium were more abundant later in the star-forming boom as more massive stars ended their lives early and enriched the galaxy with material that served as the building blocks of planets and even life on Earth.
Astronomers don't have baby pictures of our Milky Way's formative years to trace the history of stellar growth. Instead, they compiled the story from studying galaxies similar in mass to our Milky Way, found in deep surveys of the universe. The farther into the universe astronomers look, the further back in time they are seeing, because starlight from long ago is just arriving at Earth now. From those surveys, stretching back in time more than 10 billion years, researchers assembled an album of images containing nearly 2,000 snapshots of Milky Way-like galaxies.
The new census provides the most complete picture yet of how galaxies like the Milky Way grew over the past 10 billion years into today's majestic spiral galaxies. The multi-wavelength study spans ultraviolet to far-infrared light, combining observations from NASA's Hubble and Spitzer space telescopes, the European Space Agency's Herschel Space Observatory, and ground-based telescopes, including the Magellan Baade Telescope at the Las Campanas Observatory in Chile.
"This study allows us to see what the Milky Way may have looked like in the past," said Casey Papovich of Texas A&M University in College Station, lead author on the paper that describes the study's results. "It shows that these galaxies underwent a big change in the mass of its stars over the past 10 billion years, bulking up by a factor of 10, which confirms theories about their growth. And most of that stellar-mass growth happened within the first 5 billion years of their birth."
The new analysis reinforces earlier research that showed Milky Way-like galaxies began as small clumps of stars. The diminutive galaxies built themselves up by swallowing large amounts of gas that ignited a firestorm of star birth.
The study reveals a strong correlation between the galaxies' star formation and their growth in stellar mass. Observations revealed that as the star-making factories slowed down, the galaxies' growth decreased as well. "I think the evidence suggests that we can account for the majority of the buildup of a galaxy like our Milky Way through its star formation," Papovich said. "When we calculate the star-formation rate of a Milky Way galaxy and add up all the stars it would have produced, it is pretty consistent with the mass growth we expected. To me, that means we're able to understand the growth of the 'average' galaxy with the mass of a Milky Way galaxy."
The astronomers selected the Milky Way-like progenitors by sifting through more than 24,000 galaxies in the entire catalogs of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS), taken with Hubble, and the FourStar Galaxy Evolution Survey (ZFOURGE), made with the Magellan telescope.
They used the ZFOURGE, CANDELS, and Spitzer near-infrared data to study the galaxy stellar masses. The Hubble images from the CANDELS survey also provided structural information about galaxy sizes and how they evolved. Far-infrared light observations from Spitzer and Herschel helped the astronomers trace the star-formation rate.

There Could Be Lava Tubes on the Moon, Large Enough for Whole Cities

by Matt Williams on April 7, 2015

Rima Ariadaeus, a linear rile (a surface channel thought to be formed by lava) on the Moon’s surface, as photographed from Apollo 10. Credit: NASA

Every year since 1970, astronomers, geologists, geophysicists, and a host of other specialists have come together to participate in the Lunar and Planetary Science Conference (LPCS). Jointly sponsored by the Lunar and Planetary Institute (LPI) and NASA’s Johnson Space Center (JSC), this annual event is a chance for scientists from all around the world to share and present the latest planetary research concerning Earth’s only moon.
This year, one of the biggest attention-grabbers was the findings presented on Tuesday, March 17th by a team of students from Purdue University. Led by a graduate student from the university’s Department of Earth, Atmospheric and Planetary Sciences, the study they shared indicates that there may be stable lava tubes on the moon, ones large enough to house entire cities.

In addition to being a target for future geological and geophysical studies, the existence of these tubes could also be a boon for future human space exploration. Basically, they argued, such large, stable underground tunnels could provide a home for human settlements, shielding them from harmful cosmic radiation and extremes in temperature.

The Hadley Rille, at the foot of the Apennine Mountains encircling the Mare Imbrium where Apollo 15 landed. Credit: NASA/JAXA

Lava tubes are natural conduits formed by flowing lava that is moving beneath the surface as a result of a volcanic eruption. As the lava moves, the outer edges of it cools, forming a hardened, channel-like crust which is left behind once the lava flow stops. For some time, Lunar scientists have been speculating as to whether or not lava flows happen on the Moon, as evidenced by the presence of sinuous rilles on the surface.

Sinuous rilles are narrow depressions in the lunar surface that resemble channels, and have a curved paths that meanders across the landscape like a river valley. It is currently believed that these rilles are the remains of collapsed lava tubes or extinct lava flows, which is backed up by the fact they usually begin at the site of an extinct volcano.
Those that have been observed on the Moon in the past range in size of up to 10 kilometers in width and hundreds of kilometers in length. At that size, the existence of a stable tube – i.e. one which had not collapsed to form a sinuous rille – would be large enough to accommodate a major city.

For the sake of their study, the Purdue team explored whether lava tubes of the same scale could exist underground. What they found was that the stability of a lava tube depended on a number of variables- including width, roof thickness and the stress state of the cooled lava. he researchers also modeled lava tubes with walls created by lava placed in one thick layer and with lava placed in many thin layers.

The inside of a theoretical lunar lava tube, with the city of Philadelphia shown for scale. Credit: Purdue University/David Blair

David Blair, a graduate student in Purdue’s Department of Earth, Atmospheric and Planetary Sciences, led the study that examined whether empty lava tubes more than 1 kilometer wide could remain structurally stable on the moon.

“Our work is somewhat unique in that we’ve combined the talents of people from various Departments at Purdue,” Blair told Universe Today via email. “With guidance from Prof. Bobet (a civil engineering professor) we’ve been able to incorporate a modern understanding of rock mechanics into our computer models of lava tubes to see how they might actually fail and break under lunar gravity.”

For the sake of their research, the team constructed a number of models of lava tubes of different sizes and with different roof thicknesses to test for stability. This consisted of them checking each model to see if it predicted failure anywhere in the lava tube’s roof.

“What we found was surprising,” Blair continued, “in that much larger lava tubes are theoretically possible than what was previously thought. Even with a roof only a few meters thick, lava tubes a kilometer wide may be able to stay standing. The reason why, though, is a little less surprising. The last work we could find on the subject is from the Apollo era, and used a much simpler approximation of lava tube shape – a flat beam for a roof.

Mons Rümker, an extinct volcanic formation on the Moon’s surface, as imaged by the Apollo 15 spacecraft while in orbit. Credit: NASA

The study he refers to, “On the origin of lunar sinuous rilles“, was published in 1969 in the journal Modern Geology. In it, professors Greeley, Oberbeck and Quaide advanced the argument that sinuous rilles formation was tied to the collapse of lava flow tubes, and that stable ones might still exist. Calculating for a flat-beam roof, their work found a maximum lava tube size of just under 400 m.

“Our models use a geometry more similar to what’s seen in lava tubes on Earth,” Blair said, “a sort of half-elliptical shape with an arched roof. The fact that an arched roof lets a larger lava tube stay standing makes sense: humans have known since antiquity that arched roofs allow tunnels or bridges to stay standing with wider spans.”

The Purdue study also builds on previous studies conducted by JAXA and NASA where images of “skylights” on the Moon – i.e. holes in the lunar surface – confirmed the presence of caverns at least a few tens of meters across. The data from NASA’s lunar Gravity Recovery And Interior Laboratory (GRAIL) – which showed big variations in the thickness of the Moon’s crust  is still being interpreted, but could also be an indication of large subsurface recesses.

As a result, Blair is confident that their work opens up new and feasible explanations for many different types of observations that have been made before. Previously, it was unfathomable that large, stable caverns could exist on the Moon. But thanks to his team’s theoretical study, it is now known that under the proper conditions, it is least possible.

NASA’s lunar Gravity Recovery And Interior Laboratory (GRAIL) mission calculated the thickness of the moon’s crust. Credit: NASA/JPL-Caltech/S. Miljkovic

Another exciting aspect that this work is the implications it offers for future exploration and even colonization on the Moon. Already, the issue of protection against radiation is a big one. Given that the Moon has no atmosphere, colonists and agricultural operations will have no natural shielding from cosmic rays.

“Geologically stable lava tubes would absolutely be a boon to human space exploration,” Blair commented. “A cavern like that could be a really ideal place for building a lunar base, and generally for supporting a sustained human presence on the Moon. By going below the surface even a few meters, you suddenly mitigate a lot of the problems with trying to inhabit the lunar surface.”

Basically, in addition to protecting against radiation, a subsurface base would sidestep the problems of micrometeorites and the extreme changes in temperature that are common on the lunar surface. What’s more, stable, subsurface lava tubes could also make the task of pressurizing a base for human habitation easier.

“People have studied and talked about all of these things before,” Blair added, “but our work shows that those kinds of opportunities could potentially exist – now we just have to find them. Humans have been living in caves since the beginning, and it might make sense on the Moon, too!”

In addition to Melosh, Blair and Bobet, team members include Loic Chappaz and Rohan Sood, graduate students in the School of Aeronautics and Astronautics; Kathleen Howell, Purdue’s Hsu Lo Professor of Aeronautical and Astronautical Engineering; Andy M. Freed, an associate professor of earth, atmospheric and planetary sciences; and Colleen Milbury, a postdoctoral research associate in the Department of Earth, Atmospheric and Planetary Sciences.

How To Train Your Astronauts

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Training an astronaut is no easy task. Astronauts go through years of rigorous technical, health and safety training to learn simple and complex tasks for a typical four to six month mission. They develop skills in systems, robotics, spacecraft operations, space engineering activities and even learn Russian. As NASA develops deep space exploration missions on its journey to Mars, the agency is investigating current training methods in order to adapt to the longer and longer missions.

NASA astronaut Scott Kelly (center) and NASA astronaut Terry Virts participate in an extravehicular activity (EVA) maintenance training session in the Neutral Buoyancy Laboratory near NASA’s Johnson Space Center. Crew instructor Sandra Moore assists Kelly and Virts. Image Credit: NASA/James Blair

“During the Shuttle Program, astronauts trained about 5 to 8 years for a 10 to 14 day mission, with a work-timeline scripted down to the minute.” says Immanuel Barshi, a research psychologist from NASA’s Ames Research Center in Moffett Field, California, in the center’s Human Systems Integration division.
Decades of crew member research demonstrate that space can have adverse effects on people. Data suggests that the longer humans are in space, the greater the effects. On a trip to Mars, for instance, humans will be exposed to three years of microgravity and radiation; confined in an environment with three to five other people; separated from home; will experience altered day-night/light cycles; and will have three years to inevitably forget some of the training learned before leaving the planet.
Barshi’s research, a study called Training Retention, examines to what extent these aspects of a Mars mission might affect a crew member’s performance, as well as provide fresh insights into the way humans are trained for their jobs on Earth. Working with collaborators at NASA’s Johnson Space Center in Houston, Barshi will study astronaut Scott Kelly’s performance during his one-year mission aboard the International Space Station, in addition to that of other astronauts on six-month missions, and will compare results with astronauts on the ground over the same timeframe.

Astronauts Scott Kelly and Kjell Lindgren during International Space Station EVA Maintenance 9 Training at the Neutral Buoyancy Lab at the Sonny Carter Training Facility. Image Credit: NBL/Bill Brassard

In conjunction with the Center for Research on Training at the University of Colorado in Boulder, Colorado, Barshi will compare the astronaut skill retention data from space and ground with that of undergraduate students. Much of what is known on how people learn and how well they retain information or skills is based upon university research. Such comparisons are critical to the application of ground assumptions to space operations, especially how the effects of long duration space travel affect crew members.
“Researchers know that skills retained for long periods are very specific, while generalizable skills decay much faster unless continuously practiced,” says Barshi.
For example, a person can learn to enter the numbers 8675309 on a computer keypad extremely fast with excellent accuracy, and retain the skill for a long time. Ask them to do the same task, only this time using a different number sequence and the same person will be just as slow as another person who never practiced the original task. Meaning, it is the specific sequence of numbers that people remember, not the generalizable skill of entering any number.
Results from this study will not only inform choices about astronaut pre-launch, on-board and follow-on training, but they may apply to training requirements for other professional careers. Currently, high risk industries, such as oil drillers, nuclear power plant operators, medical doctors and aircraft pilots or air traffic controllers, set training requirements based upon industry consensus and not necessarily specific research.
“Hopefully we will be able to distinguish whether a shorter interval or longer interval in training works and ask whether we are excessively training people with no added benefit or saved lives, but with added costs and inefficiency,” said Barshi. “And to ask, even more importantly, are we are training people enough?”
Source: NASA