Scientists Propose Mechanism to Describe Solar Eruptions of All Sizes

NASA - Solar Dynamics Observatory (SDO) patch.

April 26, 2017

From long, tapered jets to massive explosions of solar material and energy, eruptions on the sun come in many shapes and sizes. Since they erupt at such vastly different scales, jets and the massive clouds — called coronal mass ejections, or CMEs — were previously thought to be driven by different processes.

Scientists from Durham University in the United Kingdom and NASA now propose that a universal mechanism can explain the whole spectrum of solar eruptions. They used 3-D computer simulations to demonstrate that a variety of eruptions can theoretically be thought of as the same kind of event, only in different sizes and manifested in different ways. Their work is summarized in a paper published in Nature on April 26, 2017.

A Solar Eruption in 5 Steps

Video above: Follow the evolution of a jet eruption in this video, which uses a 3-D computer simulation of the breakout model to demonstrate how a filament forms, gains energy and erupts from the sun. Video Credits: NASA’s Goddard Space Flight Center/ARMS/Genna Duberstein, producer.

The study was motivated by high-resolution observations of filaments from NASA’s Solar Dynamics Observatory, or SDO, and the joint Japan Aerospace Exploration Agency/NASA Hinode satellite. Filaments are dark, serpentine structures that are suspended above the sun’s surface and consist of dense, cold solar material. The onset of CME eruptions had long been known to be associated with filaments, but improved observations have recently shown that jets have similar filament-like structures before eruption too. So the scientists set out to see if they could get their computer simulations to link filaments to jet eruptions as well.

“In CMEs, filaments are large, and when they become unstable, they erupt,” said Peter Wyper, a solar physicist at Durham University and the lead author of the study. “Recent observations have shown the same thing may be happening in smaller events such as coronal jets. Our theoretical model shows the jet can essentially be described as a mini-CME.”

Solar scientists can use computer models like this to help round out their understanding of the observations they see through space telescopes. The models can be used to test different theories, essentially creating simulated experiments that cannot, of course, be performed on an actual star in real life.

Image above: A long filament erupted on the sun on Aug. 31, 2012, shown here in imagery captured by NASA's Solar Dynamics Observatory. Image Credits: NASA's Goddard Space Flight Center/SDO.

The scientists call their proposed mechanism for how these filaments lead to eruptions the breakout model, for the way the stressed filament pushes relentlessly at — and ultimately breaks through — its magnetic restraints into space. They previously used this model to describe CMEs; in this study, the scientists adapted the model to smaller events and were able to reproduce jets in the computer simulations that match the SDO and Hinode observations. Such simulations provide additional confirmation to support the observations that first suggested coronal jets and CMEs are caused in the same way.

“The breakout model unifies our picture of what’s going on at the sun,” said Richard DeVore, a co-author of the study and solar physicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Within a unified context, we can advance understanding of how these eruptions are started, how to predict them and how to better understand their consequences.”

The key for understanding a solar eruption, according to Wyper, is recognizing how the filament system loses equilibrium, which triggers eruption. In the breakout model, the culprit is magnetic reconnection — a process in which magnetic field lines come together and explosively realign into a new configuration.

In stable conditions, loops of magnetic field lines hold the filament down and suppress eruption. But the filament naturally wants to expand outward, which stresses its magnetic surroundings over time and eventually initiates magnetic reconnection. The process explosively releases the energy stored in the filament, which breaks out from the sun’s surface and is ejected into space.

NASA’s Solar Dynamics Observatory (SDO). Image Credit: NASA

Exactly which kind of eruption occurs depends on the initial strength and configuration of the magnetic field lines containing the filament. In a CME, field lines form closed loops completely surrounding the filament, so a bubble-shaped cloud ultimately bursts from the sun. In jets, nearby fields lines stream freely from the surface into interplanetary space, so solar material from the filament flows out along those reconnected lines away from the sun.

“Now we have the possibility to explain a continuum of eruptions through the same process,” Wyper said. “With this mechanism, we can understand the similarities between small jets and massive CMEs, and infer eruptions anywhere in between.”

Confirming this theoretical mechanism will require high-resolution observations of the magnetic field and plasma flows in the solar atmosphere, especially around the sun’s poles where many jets originate — and that’s data that currently are not available. For now, scientists look to upcoming missions such as NASA’s Solar Probe Plus and the joint ESA (European Space Agency)/NASA Solar Orbiter, which will acquire novel measurements of the sun’s atmosphere and magnetic fields emanating from solar eruptions.

Related links:

Article on Nature April 26, 2017: http://nature.com/articles/doi:10.1038/nature22050

NASA’s Solar Dynamics Observatory (SDO): https://www.nasa.gov/mission_pages/sdo/overview/index.html

NASA’s Solar Probe Plus: https://science.nasa.gov/missions/solar-probe

ESA (European Space Agency)/NASA Solar Orbiter: https://science.nasa.gov/missions/solar-orbiter

Hinode (Solar B): http://www.nasa.gov/mission_pages/hinode/index.html

Space Weather: https://www.nasa.gov/subject/3165/space-weather

Images (mentioned), Video (NASA), Text, Credits: NASA’s Goddard Space Flight Center, by Lina Tran/Rob Garner.

Greetings, Orbiter.ch

Dawn Observing Ceres; 3rd Reaction Wheel Malfunctions

NASA - Dawn Mission patch.

April 26, 2017

Mission Status Report

NASA's Dawn spacecraft is preparing to observe Ceres on April 29 from an "opposition" position, directly between the dwarf planet’s mysterious Occator Crater and the sun. This unique geometry may yield new insights about the bright material in the center of the crater.

While preparing for this observation, one of Dawn's two remaining reaction wheels stopped functioning on April 23. By electrically changing the speed at which these gyroscope-like devices spin, Dawn controls its orientation in the zero-gravity, frictionless conditions of space.

The team discovered the situation during a scheduled communications session on April 24, diagnosed the problem, and returned the spacecraft to its standard flight configuration, still with hydrazine control, on April 25. The failure occurred after Dawn completed its five-hour segment of ion thrusting on April 22 to adjust its orbit, but before the shorter maneuver scheduled for April 23-24. The orbit will still allow Dawn to perform its opposition measurements. The reaction wheel's malfunctioning will not significantly impact the rest of the extended mission at Ceres.

Image above: This artist's rendering shows NASA's Dawn spacecraft maneuvering above Ceres with its ion propulsion system. Image Credits: NASA/JPL-Caltech.

Dawn completed its prime mission in June 2016, and is now in an extended mission. It has been studying Ceres for more than two years, and before that, the spacecraft orbited giant asteroid Vesta, sending back valuable data and images. Dawn launched in 2007.

The Dawn operations team has been well prepared to deal with the loss of the reaction wheel. The spacecraft is outfitted with four reaction wheels. It experienced failures of one of the wheels in 2010, a year before it entered orbit around Vesta, and another in 2012, as it was completing its exploration of that fascinating world. (See https://dawnblog.jpl.nasa.gov/2016/01/31/dawn-journal-january-31/#RWAs). When a third reaction wheel stopped working this week, the spacecraft correctly responded by entering one of its safe modes and assigning control of its orientation to its hydrazine thrusters.

Today, Dawn's elliptical orbit will bring it from an altitude of 18,800 miles (30,300 kilometers) to 17,300 miles (27,900 kilometers) above Ceres.

The Dawn mission is managed by NASA's Jet Propulsion Laboratory in Pasadena, California, for NASA's Science Mission Directorate in Washington. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Alabama. UCLA is responsible for overall Dawn mission science. Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German Aerospace Center, Max Planck Institute for Solar System Research, Italian Space Agency and Italian National Astrophysical Institute are international partners on the mission team. For a complete list of mission participants, visit: https://dawn.jpl.nasa.gov/mission

More information about Dawn is available at the following sites:

https://www.nasa.gov/dawn

https://dawn.jpl.nasa.gov

Image (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Elizabeth Landau.

Best regards, Orbiter.ch

'Iceball' Planet Discovered Through Microlensing

NASA - Kepler Space Telescope patch.

April 26, 2017

Scientists have discovered a new planet with the mass of Earth, orbiting its star at the same distance that we orbit our sun. The planet is likely far too cold to be habitable for life as we know it, however, because its star is so faint. But the discovery adds to scientists' understanding of the types of planetary systems that exist beyond our own.

"This 'iceball' planet is the lowest-mass planet ever found through microlensing," said Yossi Shvartzvald, a NASA postdoctoral fellow based at NASA's Jet Propulsion Laboratory, Pasadena, California, and lead author of a study published in the Astrophysical Journal Letters.

Microlensing is a technique that facilitates the discovery of distant objects by using background stars as flashlights. When a star crosses precisely in front of a bright star in the background, the gravity of the foreground star focuses the light of the background star, making it appear brighter. A planet orbiting the foreground object may cause an additional blip in the star’s brightness. In this case, the blip only lasted a few hours. This technique has found the most distant known exoplanets from Earth, and can detect low-mass planets that are substantially farther from their stars than Earth is from our sun.

Image above: This artist's concept shows OGLE-2016-BLG-1195Lb, a planet discovered through a technique called microlensing. Image Credits: NASA/JPL-Caltech.

The newly discovered planet, called OGLE-2016-BLG-1195Lb, aids scientists in their quest to figure out the distribution of planets in our galaxy. An open question is whether there is a difference in the frequency of planets in the Milky Way's central bulge compared to its disk, the pancake-like region surrounding the bulge. OGLE-2016-BLG-1195Lb is located in the disk, as are two planets previously detected through microlensing by NASA's Spitzer Space Telescope.

"Although we only have a handful of planetary systems with well-determined distances that are this far outside our solar system, the lack of Spitzer detections in the bulge suggests that planets may be less common toward the center of our galaxy than in the disk," said Geoff Bryden, astronomer at JPL and co-author of the study.

For the new study, researchers were alerted to the initial microlensing event by the ground-based Optical Gravitational Lensing Experiment (OGLE) survey, managed by the University of Warsaw in Poland. Study authors used the Korea Microlensing Telescope Network (KMTNet), operated by the Korea Astronomy and Space Science Institute, and Spitzer, to track the event from Earth and space.

KMTNet consists of three wide-field telescopes: one in Chile, one in Australia, and one in South Africa. When scientists from the Spitzer team received the OGLE alert, they realized the potential for a planetary discovery. The microlensing event alert was only a couple of hours before Spitzer's targets for the week were to be finalized, but it made the cut.

With both KMTNet and Spitzer observing the event, scientists had two vantage points from which to study the objects involved, as though two eyes separated by a great distance were viewing it. Having data from these two perspectives allowed them to detect the planet with KMTNet and calculate the mass of the star and the planet using Spitzer data.

"We are able to know details about this planet because of the synergy between KMTNet and Spitzer," said Andrew Gould, professor emeritus of astronomy at Ohio State University, Columbus, and study co-author.

Although OGLE-2016-BLG-1195Lb is about the same mass as Earth, and the same distance from its host star as our planet is from our sun, the similarities may end there.

OGLE-2016-BLG-1195Lb is nearly 13,000 light-years away and orbits a star so small, scientists aren't sure if it's a star at all. It could be a brown dwarf, a star-like object whose core is not hot enough to generate energy through nuclear fusion. This particular star is only 7.8 percent the mass of our sun, right on the border between being a star and not.

Kepler Space Telescope or K2. Image Credit: NASA/JPL

Alternatively, it could be an ultra-cool dwarf star much like TRAPPIST-1, which Spitzer and ground-based telescopes recently revealed to host seven Earth-size planets. Those seven planets all huddle closely around TRAPPIST-1, even closer than Mercury orbits our sun, and they all have potential for liquid water. But OGLE-2016-BLG-1195Lb, at the sun-Earth distance from a very faint star, would be extremely cold -- likely even colder than Pluto is in our own solar system, such that any surface water would be frozen. A planet would need to orbit much closer to the tiny, faint star to receive enough light to maintain liquid water on its surface.

Ground-based telescopes available today are not able to find smaller planets than this one using the microlensing method. A highly sensitive space telescope would be needed to spot smaller bodies in microlensing events. NASA's upcoming Wide Field Infrared Survey Telescope (WFIRST), planned for launch in the mid-2020s, will have this capability.

"One of the problems with estimating how many planets like this are out there is that we have reached the lower limit of planet masses that we can currently detect with microlensing," Shvartzvald said. "WFIRST will be able to change that."

JPL manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena, California. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at the Infrared Processing and Analysis Center at Caltech. Caltech manages JPL for NASA. For more information about Spitzer, visit: http://spitzer.caltech.edu and http://www.nasa.gov/spitzer

Images (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Elizabeth Landau.

Greetings, Orbiter.ch

Taking AIM at Night-Shining Clouds: 10 Years, 10 Science Highlights

NASA - Aeronomy of Ice in the Mesosphere (AIM) patch.

April 26, 2017

Launched on April 25, 2007, NASA’s Aeronomy of Ice in the Mesosphere, or AIM, mission, has provided a wealth of new science on the dynamics and composition of Earth’s upper atmosphere. Designed to study noctilucent, or night-shining, clouds, AIM’s data have helped scientists understand a host of upper-atmosphere phenomena, from radio echoes to giant, planet-scale atmospheric waves.

“AIM started out studying clouds that form on the edge of space, about 50 miles above Earth, to understand why they form and how they vary,” said Jim Russell, principal investigator of the AIM mission at Hampton University in Hampton, Virginia. But he says that 10 years of data from AIM has far exceeded the initial expectations.  “We’ve made great strides in answering this question and learned far more about the atmosphere than we ever imagined when the mission was conceived.”

Image above: Noctilucent clouds appeared in the sky above Edmonton, Alberta, in Canada on July 2, 2011. Image Credits: NASA/Dave Hughes.

Noctilucent clouds form in Earth’s mesosphere. They’re made of ice crystals, which reflect sunlight to give off the clouds’ signature blueish glow. Though scientists had ideas about how and why these clouds form before AIM launched, the mission’s 10 years’ worth of data have confirmed their origins.

“The accepted theory was that the ice formed around meteoric smoke — very small, nanometer-scale particles that are remnants of meteors burning up in the atmosphere,” said Diego Janches, project scientist for the AIM mission at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “With AIM, we were able to study the presence and variability of that smoke.”

Over the next few years, AIM will enter a new phase of science. Because of the way the spacecraft’s orbit has shifted over time, AIM is now in an ideal position to study gravity waves, oscillations in the air usually caused by weather and winds near Earth’s surface.

“These gravity waves affect the entire circulation of the middle and upper atmosphere,” said Cora Randall, principal investigator of AIM’s Cloud Imaging and Particle Size, or CIPS, experiment at University of Colorado Boulder. “These are really important for the global atmospheric structure and composition, and even affect the polar vortex.”

Animation above: Data from NASA’s Aeronomy of Ice in the Mesosphere, or AIM, spacecraft shows the sky over Antarctica glowing electric blue due to noctilucent, or night-shining, clouds. This data was collected from Nov. 17-28, 2016. Animation Credits: NASA/HU/VT/CU-LASP/AIM/Joy Ng, producer.

AIM’s CIPS instrument can detect tiny changes in ultraviolet light reflected off of Earth’s atmosphere about 30 miles above the surface. Those tiny changes can reveal the gravity waves coming from below, much like ripples on the surface of a pond can be traced back to a dropped pebble.

AIM’s new measurements of these gravity waves, along with observations from ground-based missions and other satellite missions, will give scientists new insight into the behavior of the uppermost atmosphere at the edge of space.

“By taking these measurements at the same time, we’ll hopefully be able to link processes in the stratosphere to changes in the thermosphere even higher up,” said Janches.

AIM’s data have led to more than 200 papers on Earth’s upper atmosphere. A handful of key scientific discoveries:

- Overturning assumptions about the sun and noctilucent clouds: Observations from the 1980s and ’90s suggested that the appearance of noctilucent clouds is linked to the sun’s activity, which rises and falls in about 11-year patterns. But AIM’s data tell a different story: noctilucent clouds have been steadily increasing over the past decade, despite the sun’s regular changes in activity. The precise reason for this is still unknown.

- Noctilucent cloud and greenhouse gases: Scientists suspected that increased sightings of noctilucent clouds could be related to increasing greenhouse gases. Combining AIM’s data with 36 years of measurements from satellite instruments showed a correlation between more frequent noctilucent clouds and increases in water vapor, a greenhouse gas, and decreasing upper-atmosphere temperatures — a side effect of warming near the surface.
 
- Meteors help create noctilucent clouds: The ice crystals that form noctilucent clouds must form on a foundation of some kind. AIM’s data showed that this base is actually smoke from meteors — tiny microparticles produced when meteors burn up in Earth’s atmosphere.

- Tracking meteoric smoke: Before AIM’s launch, scientists primarily watched meteoric smoke — the tiny particles created when meteors burn up in the atmosphere — from just a few viewpoints with sounding rockets. AIM’s measurements have given scientists a new tool to watch this meteoric smoke, revealing for the first time the dynamics of how meteoric smoke moves through the atmosphere.

- Understanding the upper atmosphere: AIM helped scientists track how heat moves in the upper atmosphere, showing that heating in the mesosphere is more likely linked to circulation in the atmosphere rather than direct heating from the sun.

- Studying atmospheric waves caused by Earth’s rotation: AIM measures planetary waves, planet-scale waves caused by Earth’s rotation, that can influence weather across the globe. Over its 10-year mission, AIM has observed three of the four most extreme springtime planetary wave events seen since satellite observations began in 1978, raising questions about possible changes in the dynamics of the atmosphere.

- Teleconnection between the poles: AIM’s data showed that conditions in the stratosphere near the North Pole influence conditions in the mesosphere near the South Pole days or weeks later — even going so far as to influence the transition between seasonal conditions.

- How Earth’s weather affects the upper atmosphere: AIM’s measurements have also helped scientists track how air in the atmosphere moves vertically, as well as between the hemispheres. This helps scientists understand how events near Earth’s surface — like thunderstorms — might trigger changes in the upper atmosphere.

- Understanding the atmosphere from bottom to top: This new understanding of vertical linkages in the atmosphere was integrated into the first weather model that describes the entire atmosphere from the surface all the way to the upper mesosphere.

- The source of radar echoes: AIM solved the mystery of radar echoes in certain regions of the atmosphere during the summer. The same ice layer that produces noctilucent clouds is to blame for radar echoes, and the size of the ice crystals can even play a role.

NASA’s Aeronomy of Ice in the Mesosphere (AIM). Image Credit: NASA

Related:

NASA’s AIM website: https://www.nasa.gov/mission_pages/aim/index.html

Images (mentioned), Animation (mentioned), Text, Credits: NASA’s Goddard Space Flight Center, by Sarah Frazier/Rob Garner.

Greetings, Orbiter.ch

Weekly Recap From the Expedition Lead Scientist, Week of April 17, 2017

ISS - Expedition 51 Mission patch.

April 25, 2017

International Space Station (ISS). Image Credit: NASA

(Highlights: Week of April 17, 2017) - As the International Space Station welcomed two new crew members – NASA astronaut Jack Fischer and Russian cosmonaut Fyodor Yurchikhin -- and a resupply spacecraft, important science investigations continued, including another push to make space travelers more self-sufficient while exploring deep space.

A ground team commanded the Additive Manufacturing Facility (Manufacturing Device) on the space station to print two items over the course of the week. Installed on the station in 2015, the Manufacturing Device is a 3-D printer that uses additive manufacturing to build a part layer by layer using an engineered plastic polymer as raw material.

Image above: A Souyz rocket launches from the Baikonour Cosmodrome in Kazakhastan April 20, carrying Russian cosmonaut Fyodor Yurchikin and NASA astronaut Jack Fischer into orbit to begin their mission to the International Space Station. Image Credit: NASA.

The Manufacturing Device is another step toward a permanent manufacturing capability on the space station. It will enable the production of components and tools on demand in orbit, which will allow further research into manufacturing for long-term missions. The station crew can use it to print a variety of items to perform maintenance, build tools and repair sections in case of an emergency, leading to a reduction in cost, mass, labor and production time. Further research will also help develop this advanced technology for use on Earth.

NASA astronaut Peggy Whitson performed maintenance on the Microgravity Experiment Research Locker Incubator (MERLIN), replacing some of the desiccant inside to keep the experiments contained inside dry. MERLIN is a locker that can provide a thermally controlled environment for investigations in orbit to both extremes – both as an incubator and as a freezer. It is designed to operate with minimal crew interaction by most of the controls being commanded from the ground.

Image above: This illustration shows the configuration for conducting neurocognitive assessments for the Neuromapping study aboard the International Space Station. Image Credit: NASA.

Among the other human research investigations, Whitson completed another session with the Spaceflight Effects on Neurocognitive Performance: Extent, Longevity, and Neural Bases (NeuroMapping) investigation. This study looks at whether long-duration spaceflight causes any changes to the brain, including brain structure and function, motor control, and multi-tasking, as well as measuring how long it takes for the brain and body to recover from those possible changes. Previous research and anecdotal evidence from crewmembers returning from a long-duration mission have shown that movement control and cognition are affected in microgravity. The NeuroMapping investigation uses structural and functional magnetic resonance brain imaging to assess any changes to crewmembers after long-duration missions. This may also provide additional insight into research on the neural mechanisms associated with behavioral and physiological changes, as well as brain rehabilitation after injury.

Other human research investigations conducted this week include Actiwatch Spectrum, Fluid Shifts, Habitability, and Dose Tracker.

Progress was made on other investigations, outreach activities, and facilities this week, including Device for the study of Critical Liquids and Crystallization (DECLIC HTI-R), METEOR, Cyclops, MCDA Cool Flames Investigation, and Fast Neutron Spectrometer.

Related links:

Manufacturing Device: http://www.nasa.gov/mission_pages/station/research/experiments/2198.html

Microgravity Experiment Research Locker Incubator (MERLIN): https://www.nasa.gov/mission_pages/station/research/experiments/29.html

NeuroMapping: http://www.nasa.gov/mission_pages/station/research/experiments/1007.html

Actiwatch Spectrum: https://www.nasa.gov/mission_pages/station/research/experiments/858.html

Fluid Shifts: https://www.nasa.gov/mission_pages/station/research/experiments/1257.html

Habitability: https://www.nasa.gov/mission_pages/station/research/experiments/1772.html

Dose Tracker: http://www.nasa.gov/mission_pages/station/research/experiments/1933.html

Device for the study of Critical Liquids and Crystallization (DECLIC HTI-R): https://www.nasa.gov/mission_pages/station/research/experiments/1030.html

METEOR: https://www.nasa.gov/mission_pages/station/research/experiments/1323.html

Cyclops: https://www.nasa.gov/mission_pages/station/research/experiments/1014.html

MCDA Cool Flames Investigation: https://www.nasa.gov/mission_pages/station/research/experiments/1947.html

Fast Neutron Spectrometer: https://www.nasa.gov/mission_pages/station/research/experiments/2103.html

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Images (mentioned), Text, Credits: NASA/Kristine Rainey/Jorge Sotomayor, Lead Increment Scientist Expeditions 51 & 52.

Greetings, Orbiter.ch

Countdown to Cassini's Grand Finale

ESA - Cassini Mission to Saturn logo.

25 April 2017

After nearly 13 years in orbit around Saturn, the international Cassini–Huygens mission is about to begin its final chapter: the spacecraft will perform a series of daring dives between the planet and its rings, leading to a dramatic final plunge into Saturn's atmosphere on 15 September.

On 22 April, Cassini successfully executed its 127th and final close flyby of Saturn's largest moon, Titan.

Cassini grand finale

The manoeuvre put the spacecraft onto its ’grand finale’ trajectory: a series of 22 orbits, each lasting about a week, drawing closer to Saturn and passing between the planet's innermost rings and its outer atmosphere. The first crossing of the ring plane will occur on 26 April.

With the repeated dives in this yet unvisited region, the mission will conclude its journey of exploration by collecting unprecedented data to address fundamental questions about the origin of Saturn and its ring system.

Launched in 1997, the Cassini-Huygens spacecraft embarked on a seven-year voyage across the Solar System, eventually reaching Saturn in July 2004. Several months later, the Cassini orbiter released ESA’s Huygens probe, which landed on Titan on 14 January 2005 – the first landing in the outer Solar System.

The mission has greatly contributed to our understanding of the Saturnian environment, including the giant planet’s system of rings and moons.

Titan flyby 22 April 2017

Combining the data collected in situ by Huygens and the observations performed by Cassini during flybys of Titan, the mission revealed the atmospheric processes of this moon and their seasonal evolution, as well as the surface morphology and interior structure, which may include a liquid water ocean.

Enshrouded by a thick nitrogen-dominated atmosphere and partly covered by lakes and rivers, Titan has a weather and hydrological cycle that bears some interesting similarities to Earth. However, there are important differences: the key component there is not water, like on our planet, but methane, and the temperature is very low, around –180°C at the surface.

Over its 13-year mission, Cassini will have covered about half of Saturn’s orbit, in which the planet takes 29 years to circle the Sun. This means that the spacecraft has monitored two seasons on Titan, an object that can teach us much on the past and the future of Earth.

Another of Cassini's breakthroughs was the detection of a towering plume of water vapour and organic material spraying into space from warm fractures near the south pole of Saturn's icy moon, Enceladus. These salt-rich jets indicate that an underground sea of liquid water is lurking only a few kilometres below the moon's icy surface, as confirmed by gravity and rotation measurements.

Enceladus jets

A recent analysis of data collected during flybys of Enceladus with the Cassini Ion Neutral Mass Spectrometer also revealed hydrogen gas in the plume, suggesting that rock might be reacting with warm water on the seafloor of the moon's subsurface ocean. This hydrothermal activity could provide a chemical energy source for life, enabling non-photosynthetic biological processes similar to the ones found near the hydrothermal vents on the Earth’s ocean floor and pointing to the potential habitability of Enceladus' underground ocean.

Following over a decade of ground-breaking discoveries, Cassini is now approaching its end. With little fuel left to correct the spacecraft trajectory, it has been decided to end the mission by plunging it into Saturn’s atmosphere on 15 September 2017. In the process, Cassini will burn up, satisfying planetary protection requirements to avoid possible contamination of any moons of Saturn that could have conditions suitable for life.

The grand finale is not only a spectacular way to complete this extraordinary mission, but will also return a bounty of unique scientific data that was not possible to collect during the previous phases of the mission. Cassini has never ventured into the area between Saturn and its rings before, so the new set of orbits is almost like a whole new mission.

These close orbits will be inclined 63 degrees with respect to Saturn's equator and will provide the highest resolution observations ever achieved of the inner rings and the planet's clouds. The orbits will also give the chance to examine in situ the material in the rings and plasma environment of Saturn.

Grand finale orbits

With its radio science investigation, Cassini will measure Saturn's gravitational field as close as 3000 km from Saturn's upper cloud layers, greatly improving the current models of the planet's internal structure and winds in its atmosphere. Scientists expect the new data will also allow them to disentangle the gravity of the planet from the tiny pull exerted on the spacecraft by the rings, estimating the total mass of the rings to unprecedented accuracy. ESA ground stations in Argentina and Australia will help receive Cassini's radio science data, providing a series of 22 tracking passes during the grand finale.

The grand finale orbits will also probe the planet's magnetic field at similarly close distances. Previous observations have shown that the magnetic field is weaker than expected, with the magnetic axis surprisingly well aligned with the planet's rotation. New data to be collected by the Cassini magnetometer will provide insights to understand why this is so and where the sources of magnetic field are located, or whether something in Saturn's atmosphere has been obscuring the true magnetic field from Cassini until now.

Cassini between Saturn and the rings

While crossing the ring plane, Cassini's Cosmic Dust Analyzer will directly sample the composition of dust particles from different parts of the ring system, whereas the Ion Neutral Mass Spectrometer will sniff the upper atmosphere layers of Saturn to analyse molecules escaping from the atmosphere as well as water-based molecules that originate from the rings.

“At last, we have now reached the final and most audacious phase of this pioneering mission, pushing the spacecraft once again into unexplored territory,” says Nicolas Altobelli, ESA Cassini project scientist.

“We are looking forward to the flow of exciting new data that Cassini will send back in the coming months.”

Notes for Editors

Cassini–Huygens is a cooperative project of NASA, ESA and ASI, the Italian space agency.

Related articles:

Cassini Completes Final -- and Fateful -- Titan Flyby
http://orbiterchspacenews.blogspot.ch/2017/04/cassini-completes-final-and-fateful.html

Cassini Mission Prepares for 'Grand Finale' at Saturn
http://orbiterchspacenews.blogspot.ch/2017/04/cassini-mission-prepares-for-grand.html

Related links:

NASA JPL Cassini site: http://saturn.jpl.nasa.gov/

Italian Space Agency: http://www.asi.it/en

ESA Cassini-Huygens: http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Cassini-Huygens in depth: http://sci.esa.int/huygens

Images, Animation, Text, Credits: ESA/Markus Bauer/Nicolas Altobelli/NASA/JPL-Caltech/Erick Sturm/Space Science Institute.

Best regards, Orbiter.ch

Sequencing the Station: Investigation Aims to Identify Unknown Microbes in Space

ISS - International Space Station logo.

April 25, 2017

Building on the ability to sequence DNA in space and previous investigations, Genes in Space-3 is a collaboration to prepare, sequence and identify unknown organisms, entirely from space. When NASA astronaut Kate Rubins sequenced DNA aboard the International Space Station in 2016, it was a game changer. That first-ever sequencing of DNA in space was part of the Biomolecule Sequencer investigation.

Although it’s not as exciting as a science fiction movie may depict, the walls and surfaces of the space station do experience microbial growth from time to time. Currently, the only way to identify contaminants is to take a sample and send it back to Earth.

Image above: NASA astronaut Kate Rubins poses for a picture with the minION device during the first sample initialization run of the Biomolecular Sequencer investigation. Image Credit: NASA.

“We have had contamination in parts of the station where fungi was seen growing or biomaterial has been pulled out of a clogged waterline, but we have no idea what it is until the sample gets back down to the lab,” said Sarah Wallace, NASA microbiologist and the project’s principal investigator at the agency’s Johnson Space Center in Houston.

“On the ISS, we can regularly resupply disinfectants, but as we move beyond low-Earth orbit where the ability for resupply is less frequent, knowing what to disinfect or not becomes very important,” said Wallace.

Developed in partnership by NASA’s Johnson Space Center and Boeing, this ISS National Lab sponsored investigation will marry two pieces of existing spaceflight technology, miniPCR and the MinION, to change that process, allowing for the first unknown biological samples to be prepared, sequenced and then identified in space.

Image above: NASA astronaut Kate Rubins not only became the first person to sequence DNA in space, but the sequenced more than a billion bases during her time aboard the space station. Image Credit: NASA.

The miniPCR (polymerase chain reaction) device was first used aboard the station during the Genes in Space-1, and, soon to be Genes in Space-2 investigations, student-designed experiments in the Genes in Space program. Genes in Space-1 successfully demonstrated the device could be used in microgravity to amplify DNA, a process used to create thousands of copies of specific sections of DNA. The second investigation arrived at the space station on April 22, and will be tested this summer.

Next came the Biomolecule Sequencer investigation, which successfully tested the MinION’s ability to sequence strands of Earth-prepared DNA in an orbiting laboratory.

“What the coupling of these different devices is doing is allowing us to take the lab to the samples, instead of us having to bring the samples to the lab,” said Aaron Burton, NASA biochemist and Genes in Space-3 co-investigator.

Crew members will collect a sample from within the space station to be cultured aboard the orbiting laboratory. The sample will then be prepared for sequencing, in a process similar to the one used during the Genes in Space-1 investigation, using the miniPCR and finally, sequenced and identified using the MinION device.

Image above: Student Anna-Sophia Boguraev, winner of the Genes in Space competition, is pictured with the miniPCR device. The miniPCR will be used with the minION to prepare, sequence and identify a microorganism from start to finish aboard the space station. Image Credit: NASA.

“The ISS is very clean,” said Sarah Stahl, microbiologist and project scientist. “We find a lot of human-associated microorganisms - a lot of common bacteria such as Staphylococcus and Bacillus and different types of familiar fungi like Aspergillus and Penicillium.”

In addition to identifying microbes in space, this technology could be used to diagnose crew member wounds or illnesses in real time, help identify DNA-based life on other planets and help with other investigations aboard the station.

“The Genes in Space-3 process will increase the scientific capacity of the ISS by facilitating state-of-the-art molecular biology research for both current and next generation ISS researchers,” said Kristen John, NASA aerospace engineer and Genes in Space-3 project engineer. “The team has put a strong focus on generating a spaceflight-certified catalog of general laboratory items and reagents, and developing common methods and easily customizable reaction conditions for miniPCR and the MinION to enable other ISS researchers to use this technology.”

Cosmic Carpool: DNA To Go

This process will give scientists on the ground real-time access to the experiments going on in space, allowing for more accuracy and a more efficient use of the time on the space station.

“If you could get a snapshot of the molecular signatures of your research as it was occurring on the ISS, how would you change your experiment?” said Wallace. “Would you change your time points? Provide a different nutrient? Alter growth conditions? You can imagine how, if you had that data, you could adjust your experiment to enhance the insight being gained.”

Closer to home, this process can be used to provide real-time diagnosis of viruses in areas of the world where access to a laboratory may not be possible.

The ISS National Laboratory is managed by the Center for the Advancement of Science in Space (CASIS). For more information about research happening aboard the space station, follow https://twitter.com/ISS_Research.

Related links:

Biomolecule Sequencer: https://www.nasa.gov/mission_pages/station/research/experiments/2181.html

miniPCR: https://www.nasa.gov/mission_pages/station/research/experiments/1913.html

Genes in Space-1: https://www.nasa.gov/mission_pages/station/research/experiments/1913.html

Genes in Space-2: https://www.nasa.gov/mission_pages/station/research/experiments/2437.html

Genes in Space-3: https://www.nasa.gov/mission_pages/station/research/experiments/2461.html

Center for the Advancement of Science in Space (CASIS): http://www.iss-casis.org/

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Images (mentioned), Video, Text, Credits: NASA/Kristine Rainey/JSC/Jenny Howard.

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