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Thursday August 17th 2017

‘Solar System’

The Moons of the Solar System

More Questions Than Answers

Europa Moon of Jupiter Europa – Moon of Jupiter. Credit NASA

Think of our solar system, and for most of us the first thing to come to mind would be the eight planets orbiting our Sun. But perhaps even more interesting are the moons which orbit the planets. Our Moon seems to be a lifeless body, with hardly any atmosphere and no dynamic activity. But the more data we collect, and the more we learn about its formation, the more fascinating it becomes. The same is true of the moons of the outer gas giants, some of which are comparable in size to the Moon. Little was known about these bodies until we began to send spacecraft armed with a host of sensors in order to analyse them in much greater detail. Each has its own uniquely distinctive characteristics in terms of overall composition, and their widely diverse range of surface features give tantalizing clues to what is going on beneath. The image below shows the size of the Earth’s Moon in relation to other moons and planets in the Solar System.

Moons of the Solar System Moons of the Solar System / Credit NASA

Galileo and the Beginning of Modern Astronomy

In 1610 Italian astronomer Galileo Galilei discovered the four largest moons of Jupiter; Io, Europa, Ganymede and Callisto. He used a homemade telescope to observe the motion of these bodies, which he first took to be stars. But after a few weeks he realized that they never left the vicinity of Jupiter, and they changed position in relation to each other and the planet. Galileo therefore concluded that they must be planetary bodies in orbit around Jupiter. This discovery, along with his measurements of the phases of Venus, proved that not everything in the Universe revolves around the Earth, and led to conflict with the Catholic Church by refuting the geocentric view of the Solar System. But importantly for science, his work also marked the beginning of modern astronomy.

Jupiter-moons_475px All that’s required to see the Galilean moons of Jupiter is either a good pair of binoculars or a small telescope. Credit: Jan Sandberg, www.desert-astro.com

The Inner Solar System

Phobos_Deimos_475px Phobos (left) and Deimos (right), Moons of Mars. Credit NASA

Both Mercury and Venus have no moons at all. One theory for this is that if they ever possessed a moon in the past, it would have eventually been stolen by either the gravitational pull of the Sun or the gravitational pull of the host planet. Then there’s Mars which has two moons, Phobos and Deimos. These are very small bodies, with Phobos having a diameter of 22.2 km and Deimos 12.4 km, so they haven’t got enough mass to enable them to form into the roughly spherical shapes that larger bodies are able to do. The orbital radius of Phobos is just 9,377 km, with an orbital period of 0.32 days. It is being pulled 1.8 m closer to Mars every century, and so will eventually either crash into the planet or break up and form a ring of material around it. Deimos, on the other hand, has an orbital radius of 23,460 km, and is gradually moving in the opposite direction, away from Mars, just like our own Moon is moving away from the Earth. So one day both Deimos and the Moon will cease to be influenced by the pull of their host planets and be set free into space.

The Outer Solar System

Io, moon of Jupiter shown with plume. Credit: NASAIt seems reasonable to assume that the further from the Sun the colder the temperature of the bodies that exist there. At Jupiter, which lies five times further from the Sun than the Earth, the average surface temperature of its moons is -170°C. At Saturn the average surface temperature is -200°C, at Uranus -210°C, and at Neptune -235°C. Before it was possible to closely inspect the moons of the outer planets in any great detail, scientists assumed that, due to these low temperatures, they would be cold, lifeless, inactive bodies. But since Voyager 1, launched in 1977, the Galileo mission, launched in 1989, and Cassini-Huygens in 1997, it has become clear that their theories were very far from the truth. Io for example, the innermost of the four Galilean moons of Jupiter, is the most volcanically active body in the solar system. Whilst having an average surface temperature of -130°C, its volcanoes can reach 1,650°C. It is covered in sulfur due to the hundreds of active volcanoes on its surface, and has lava lakes, floodplains of liquid rock and plumes of sulfur reaching as high as 300km. The above image (credit: NASA) of Io showing an active plume from a volcano. Io’s colorful appearance is due to various materials produced by its volcanism, including silicates, sulfur and sulfur dioxide.

Resonance

The reason for Io’s volcanic activity is due to the orbital resonance of three of the four Galilean moons, meaning that their orbital periods are multiples of each other. Io revolves around Jupiter four times in the same period it takes Europa to revolve twice and Ganymede to revolve once. This regular alignment results in a gravitational pull which has caused their orbital paths around Jupiter to become elliptical. This in turn creates immense tidal forces, causing the physical rock on Io’s surface to rise up and down a hundred meters during the course of each Io day, or about every 42 hours. A huge amount of heat is therefore generated, which is enough to melt a large proportion of Io’s interior and bring about the conditions we have observed on its surface from pictures relayed by Voyager 1 in the late seventies and the Galileo mission in the late 1990’s and early 2000’s. Resonance is common in the solar system, and accounts for the geysers and the jets on Enceladus for example, and the liquid water ocean beneath the surface of Europa.

Cryovolcanism

Image taken by NASA’s Cassini probe of jets of water ice being emitted from the surface of Enceladus. Credit: NASA/JPL/SSI Image taken by NASA’s Cassini probe of jets of water ice being emitted from the surface of Enceladus. Credit: NASA/JPL/SSI

Volcanism does not only occur on rocky bodies like Io. In March 2006 the Cassini probe observed icy jets being emitted from the south pole of Enceladus, a moon of Saturn. The volcanoes erupting these jets were however not spewing out molten rock. When Cassini flew through the plume of one of these emissions, it detected predominantly salty water-ice, with small amounts of carbon dioxide, ammonia, methane and other hydrocarbons. The contaminants lower the melting temperature of the ice on the crust of Enceladus, allowing the generation of cryomagma, which can be erupted in plumes reaching hundreds of kilometers above its surface. Other icy moons exhibiting cryovolcanism include Ariel and Miranda orbiting Uranus, and Triton, the largest moon of Neptune.

Is There Life in the Solar System?

Mars has traditionally been the place to look for alien life in the solar system, but the icy moons of the outer planets are exciting for scientists to study because their surfaces are comprised of large amounts of water ice. Although solid at the surface, it has been proven that vast amounts of liquid water can exist underneath. The Galileo mission to Jupiter gave evidence that Europa has an ocean of water beneath its icy surface totaling more than all the oceans, rivers and lakes existing on the Earth. And where there’s water there’s the potential for life, at least life as we know it. Tidal distortion has created cracks on the surface of Europa, enabling liquid water to escape to the surface. These could be the places where life is most likely to occur, as sunlight could create the conditions for photosynthesis to take place. Other places with the potential for life are Ganymede, Enceladus and Titan, Saturn’s biggest moon.

Plate tectonics on Europa. Image Credit: NASA Plate tectonics on Europa. Image Credit: NASA

But life can also be created without the need for sunlight. At the bottom of our oceans on Earth, hydro-thermal vents exist that harbor microbes which, in a process called chemosynthesis, convert chemicals from the vent into usable energy. So why can’t this same process take place elsewhere in the solar system, or elsewhere in the Universe for that matter?

Future Exploration

NASA’s New Horizons spacecraft is one of the latest ongoing missions to explore the solar system. It is on its way to a rendezvous with the newly termed dwarf planet Pluto and its moon Charon, both members of the vast region beyond Neptune known as the Kuiper Belt. Launched in 2006, and moving at almost one million miles per day, it will reach Pluto in summer 2015, armed with much more state of the art sensors than earlier missions. For instance, it will include LORRI, one of the highest resolution telescopes ever sent into space. Scientists believe that the Kuiper Belt contains a totally different class of world than the rest of the Solar System, so to better understand it, we need to understand worlds like Pluto and Charon.
In 2022 the European Space Agency is planning to launch the Jupiter Icy Moons Explorer (JUICE), which will study Ganymede, Europa and Callisto, and their potential for containing life. NASA too is hoping to launch its own mission to Europa in 2022, called the Europa Clipper. It will fly down to within 25km of its surface, and may even include a lander. So the future of space exploration is alive and well, with plenty of exciting encounters to look forward to.

Further Sources

NASA JPL Live http://ustre.am/onbo. NASA Scientists discuss the future mission to Europa

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Asteroid Mining

Asteroid Itokawa
Near Earth Asteroid Itokawa. A likely candidate for future mining opportunities. Credit JAXA

Look back in history and you will see that the motivation behind huge investments in exploration and transportation has been the need for resources.  The American settlers headed west in their search of gold, oil and timber, and the Europeans headed east along the Silk Road and the spice trade routes.  Now, a company based in Seattle, Washington, plans to head away from Earth and into space in search of the precious resources to be found within the thousands of asteroids existing in orbits relatively close to our planet.

The company, Planetary Resources Inc, founded by Eric Anderson and Peter Diamandis, has attracted a group of investors and advisers including Eric Schmidt and Larry Page of Google, and film director James Cameron.  The ultimate goal is to exploit the valuable resources which asteroids can offer, and the biggest challenge is to achieve this within a budget which makes the whole project cost effective.

Why is asteroid mining such an exciting proposition

How an asteroid could be captured and moved into a more convenient orbit. Credit Planetary Resources

Asteroids contain an abundance of valuable resources including platinum, gold, iron, nickel, rare earth metals and water.  At present around 9,000 known asteroids travelling in an orbit close to Earth’s have been identified, with around 1,000 new ones being discovered each year, all of which as easy to reach as the moon.  And because they are much smaller than the moon the lower gravitational force will mean that landing and taking off will be less of a problem.  Unlike the Earth, heavier metals are distributed evenly throughout an asteroid’s mass rather than closer to the core, and as an added attraction the presence of these materials will often be found in much higher concentrations than on Earth.  For instance, it has been estimated that a one kilometer diameter asteroid could contain about 7,500 tons of platinum, worth more than $150 billion.

Rare Earth metals

Despite their name, rare earth metals are fairly common in the Earth’s crust, but the fact that they are so widely scattered makes them difficult to mine. So finding a viable means of harvesting them from space will potentially be a highly profitable business.  Added to this, around 95% of the world’s supply of rare earth metals presently comes from China, who have decided to cut back on their exports in order to accommodate their own rapidly expanding industrial needs.

Platinum group metals

Platinum group metals do not occur naturally in the Earth’s crust, but are present due to earlier meteorite impacts.  A meteorite is simply a piece of asteroid which has fallen to Earth, so the study of meteorites gives geologists a good idea of the most suitable types of asteroid to choose as candidates for mining.

Which are the most likely candidates?

An artist’s impression of the Asteroid Belt. Credit NASA

The vast majority of asteroids are located in the region of our Solar System between Mars and Jupiter called the Asteroid Belt, or Main Belt.  They range in size from around half a mile across to about 600 miles in diameter, and were created at the birth of the Solar System, 4.6 billion years ago.  To put it into perspective, the total mass of all known asteroids, more than half a million in all, is about 4% that of the moon.  Due to the gravitational influence of Jupiter some have orbits which carry them close to Earth, in which case they are called Near Earth Objects, or Near Earth Asteroids.  And these are the asteroids which Planetary Resources intend to study and ultimately exploit.

 

How are asteroids classified?

 In broad terms there are three classifications of asteroid based on their composition:

  • C-type, which are the most common, are carbonaceous, and consist of clay and silicate rocks.  They exist furthest from the Sun, and so have been least altered by heat, meaning that they are the most ancient. Due to the fact that some have never even reached temperatures above 50°C, it is estimated they can contain up to 22% water.
  • S-type or silaceous asteroids are made up primarily of stony materials and nickel-iron.  They inhabit the inner Asteroid Belt.
  • M-type, or metallic, are made up mostly of nickel-iron, and are found in the middle region of the Asteroid Belt.

 

2005-YU55, a C-type asteroid. Credit NASA

 

What are the challenges?

 The greatest challenge to Planetary Resources is to build commercially available robotic spacecraft which are at least an order of magnitude cheaper than those currently in use.  Unlike governments, failure can be accepted during the development process, and the goal is to build the crafts in an assembly line fashion in order to drive down costs.  The project will be carried out in stages, with the first phase already underway, and it is hoped that by the middle of next decade mankind will be reaping the benefits of the abundant resources that asteroids have to offer.

 The technology 

  • The Arkyd Series 100 – Leo Space Telescope.  Due for launch within the next two years, its job will be to analyse NEOs in order to determine the most likely candidates for future exploitation.  Techniques such as spectroscopy and radar technology will be used to determine properties such as the asteroid’s chemical composition, orbit, rotation, size, shape and metal concentration.  Due to its relatively low cost and its potential usefulness in a vast number of applications, the Leo will be of interest to the scientist and private citizen alike.  The sale of these crafts will therefore enable Planetary Resources to gain revenue in order to achieve its future objectives.
  • The Arkyd Series 200 – Interceptor.  The intention is for this craft to hitch a ride on a geostationary satellite in order to analyse asteroids at more close quarters.  Future advancements in micro-propulsion and imaging techniques will be utilised to enable the craft to get close enough to obtain high resolution data.  Two or more Interceptors working together will ensure that the data is collected as quickly and efficiently as possible.
  • The Arkyd Series 300 – Rendezvous Prospector.  This phase of the project will involve focusing on asteroids much deeper in space.  Laser communication technology will be used  to determine shape, rotation, density, and surface and sub-surface composition.  The Prospector’s capability as a low cost interplanetary spacecraft should also attract customers such as NASA and other scientific establishments.

    Arkyd Series100 - LEO Space Telescope. Credit Planetary Resources

 

Mining

After all the prospecting has taken place, the most exciting phase of the project can then be carried out, the actual mining of the precious resources.  Initially the most important resource available in space will be water.  Apart from being essential to sustain life, it can also be split into hydrogen and oxygen to create fuel to enable spacecraft to travel further into space.  This would allow us to build refuelling stations in order to reach more distant asteroids and aid future manned exploration of the solar system.  For this reason the first targeted asteroids will most likely be C-type.

What methods will be used?

Could this be the future of asteroid mining? Credit Kevin Hand for Popular Science, 2012

The technology needed to carry out the mining process has not yet been developed, but possible methods have been suggested.  A device similar to a snow blower, anchored to the surface, could be used to collect loose rubble by using a spinning blade to fling the material through a chute and into a high-strength bag.  Many of the mining methods will be similar to those used on Earth, and will consist of drilling, blasting, cutting and crushing.  Extraction of individual materials, depending upon their properties, will be achieved by either chemical or physical means.  Water can be extracted by heating the solid material, capturing the vapour and then distilling it; electrolysis of molten silicates would produce oxygen, iron and other alloys; and a method called the Mond process could be used to extract nickel.  As well as being used for creating industrial wealth on Earth, these raw materials could also be used to actually build structures in space.  Dozens of other processes are being considered, and meteorites are the perfect objects to experiment with on Earth.

 

Within reach!

The idea of landing a robotic craft onto an asteroid in order to extract its precious materials may at first seem the stuff of science fiction.  But the more scientists get to grips with the technology necessary to achieve it, the more likely it is that science fiction will soon become science fact.

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Positions of Planets

Saturn, credit: Nasa
Saturn, image credit: NASA

The tables offer monthly positions of the four brightest planets: Venus, Mars, Jupiter and Saturn. Note, that a constellation may not be visible during the night.  Another good monthly reference is created by the folks of SkyMaps.  It shows monthly events and locations of planets and can be downloaded as pdf for printing.  Also Sky View Cafe and Astronomy Magazine offer very nice online planetaria that show positions of planets and provide a wealth of other information. Both need Java installed on your computer.

2012 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus AQR PSC ARI TAU TAU TAU TAU GEM CNC LEO VIR LIB
Mars VIR LEO LEO LEO LEO LEO VIR VIR LIB SCO SGR SGR
Jupiter ARI ARI ARI ARI TAU TAU TAU TAU TAU TAU TAU TAU
Saturn VIR VIR VIR VIR VIR VIR VIR VIR VIR VIR VIR VIR
                         
2013 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus SGR CAP AQR ARI TAU GEM LEO VIR VIR OPH SGR SGR
Mars CAP AQR PSC PSC ARI TAU GEM GEM CNC LEO LEO VIR
Jupiter TAU TAU TAU TAU TAU TAU GEM GEM GEM GEM GEM GEM
Saturn LIB LIB LIB VIR VIR VIR VIR VIR LIB LIB LIB LIB
                         
2014 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus SGR SGR CAP AQR PSC ARI TAU CNC LEO VIR LIB SGR
Mars VIR VIR VIR VIR VIR VIR VIR LIB SCO OPH SGR CAP
Jupiter GEM GEM GEM GEM GEM GEM CNC CNC CNC LEO LEO LEO
Saturn LIB LIB LIB LIB LIB LIB LIB LIB LIB LIB LIB LIB
                         
2015 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus CAP AQR PSC TAU GEM CNC LEO LEO CNC LEO VIR LIB
Mars AQR PSC PSC ARI TAU TAU GEM CNC LEO LEO VIR VIR
Jupiter LEO CNC CNC CNC CNC LEO LEO LEO LEO LEO LEO LEO
Saturn SCO SCO SCO SCO SCO LIB LIB LIB LIB SCO SCO OPH
                         
2016 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus OPH SGR AQR PSC ARI TAU CNC LEO VIR LIB SGR CAP
Mars VIR LIB SCO OPH SCO LIB LIB SCO OPH SGR CAP AQR
Jupiter LEO LEO LEO LEO LEO LEO LEO VIR VIR VIR VIR VIR
Saturn OPH OPH OPH OPH OPH OPH OPH OPH OPH OPH OPH OPH
                         
2017 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus AQR PSC PSC PSC PSC ARI TAU GEM LEO VIR LIB OPH
Mars AQR PSC ARI TAU TAU GEM GEM CNC LEO VIR VIR VIR
Jupiter VIR VIR VIR VIR VIR VIR VIR VIR VIR VIR LIB LIB
Saturn OPH OPH SGR SGR SGR OPH OPH OPH OPH OPH OPH SGR
                         
2018 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus SGR AQR PSC ARI TAU CNC LEO VIR VIR VIR VIR LIB
Mars LIB OPH SGR SGR CAP CAP CAP CAP CAP CAP AQR AQR
Jupiter LIB LIB LIB LIB LIB LIB LIB LIB LIB LIB LIB OPH
Saturn SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR
                         
2019 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus OPH SGR CAP AQR PSC TAU GEM LEO VIR LIB OPH SGR
Mars PSC ARI ARI TAU TAU GEM CNC LEO LEO VIR VIR LIB
Jupiter OPH OPH OPH OPH OPH OPH OPH OPH OPH OPH OPH SGR
Saturn SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR
                         
2020 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus AQR PSC ARI TAU TAU TAU TAU GEM CNC LEO VIR LIB
Mars OPH SGR SGR CAP AQR AQR CET PSC PSC PSC PSC PSC
Jupiter SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR SGR
Saturn SGR SGR SGR CAP CAP CAP SGR SGR SGR SGR SGR SGR
                         
2021 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus SGR CAP AQR ARI TAU GEM LEO VIR VIR OPH SGR SGR
Mars ARI ARI TAU TAU GEM CNC LEO LEO VIR VIR LIB SCO
Jupiter CAP CAP CAP CAP AQR AQR AQR AQR CAP CAP CAP AQR
Saturn CAP CAP CAP CAP CAP CAP CAP CAP CAP CAP CAP CAP
                         
2022 Jan Feb Mar Apr May June Jul Aug Sep Oct Nov Dec
Venus SGR SGR CAP AQR PSC ARI TAU CNC LEO VIR LIB SGR
Mars OPH SGR CAP AQR AQR PSC ARI TAU TAU TAU TAU TAU
Jupiter AQR AQR AQR PSC PSC PSC CET CET PSC PSC PSC PSC
Saturn CAP CAP CAP CAP CAP CAP CAP CAP CAP CAP CAP CAP

 

Constellation Maps

 
AQR- Aquarius ARI – Aries CAP – Capricornus
CET – Cetus CNC – Cancer GEM – Gemini
LEO – Leo LIB – Libra OPH – Ophiuchus
PSC – Pisces SCO – Scorpius SGR – Sagittarius
TAU – Taurus VIR – Virgo  
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Voyager Explores Stagnation Region

Voyager Spacecraft
Voyager Spaceraft, Image credit : NASA

 NASA’s Voyager 1 has entered a new region between our solar system and interstellar space, which scientists are calling the stagnation region. The inner edge of this region is located about 113 astronomical units (10.5 billion miles or 16.9 billion kilometers) from the sun. Voyager 1 is currently about 119 astronomical units (11 billion miles or 17.8 billion kilometers) from the sun. The exact distance to the outer edge is unknown.

Voyager 1 spacecraft has entered the stagnation region.
Artist's concept of Voyager 1 spacecraft has entered the stagnation region. Image credit: NASA/JPL-Caltech

The stagnation region is considered to be a kind of cosmic purgatory according to data obtained from the spacecraft during the last year. In it, the wind of charged particles streaming out from our sun has calmed, but our solar system’s magnetic field has piled up, and higher-energy particles from inside our solar system appear to be leaking out into interstellar space. At the same time, Voyager has detected a 100-fold increase in the intensity of high-energy electrons from elsewhere in the galaxy diffusing into our solar system from outside, which is another indication of the approaching boundary

There is not much time left to find out what the space between stars is. The spacecraft has passed through the heliosheath, the outer shell of the sun’s sphere of influence and is still within the heliosphere, the bubble of charged particles the sun blows around itself. Interstellar space begins at the heliopause, and scientists estimate Voyager 1 will cross this frontier around 2015. 

Interstellar Flow
Stream of interstellar charged particles, Image credit: NASA

 Voyager’s magnetometer detected a doubling in the intensity of the magnetic field in the stagnation region which shows that inward pressure from interstellar space is compacting it. “We are evidently traveling in completely new territory. Scientists had suggested previously that there might be a stagnation layer, but we weren’t sure it existed until now.,” said Rob Decker, a Voyager Low-Energy Charged Particle Instrument co-investigator at the Johns Hopkins University Applied Physics Laboratory in Laurel, MD.

Voyager - The Sounds of Earth - Golden Record
Voyager Golden Record, Image credit: NASA

Launched in 1977, Voyager 1 is about 18 billion kilometers from the sun. A signal from the ground, traveling at the speed of light, takes about 16 hours one way to reach the spacecraft. Voyager carries aboard recorded messages from Earth on golden phonograph record – 12-inch, gold-plated copper disk that contains images and natural sounds, spoken greetings in 55 languages and musical selections from different cultures and eras.

Credit: NASA/JPL-Caltech
Source URL: http://www.nasa.gov/mission_pages/voyager/index.html

 

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Mars Express – Scientific Highlights

Mars Express - Credit: ESA/Medialab
Mars Express - Credit: ESA/Medialab

The following DLR article talks about measurements and scientific experiments performed by Mars Express mission.

By: DLR

This success story began eight years ago, with the launch of a Soyuz carrier rocket from the Baikonur Cosmodrome in Kazakhstan that sent the Mars Express spacecraft on its journey to our planetary neighbour. Since then, a wealth of information about Mars, its surface, subsurface and atmosphere has led to a completely new view of the Red Planet.

The Infrared Mineralogical Mapping Spectrometer (OMEGA) has identified phyllosilicates (sheet silicates) on the surface of Mars. Such minerals are rich in iron and aluminium and arise as a result of the prolonged effect of water on volcanic rock. This discovery has led to a new view of the history of Mars; in its early days, at least, vast amounts of liquid water shaped its surface.

Water ice in the northern polar region of Mars - perspective colour view. Credit: ESA/DLR/FU Berlin (G. Neukum).
Water ice in the northern polar region of Mars – perspective colour view. Credit: ESA/DLR/FU Berlin (G. Neukum).

Using images from the High Resolution Stereo Camera (HRSC) operated by DLR, the HRSC team has determined that volcanism on Mars lasted for a long period of time, until the most recent geological past. Consequently the youngest lava concretions in the summit caldera of Olympus Mons are just 100 million years old. In fact, there may still be residual activity here and at a few volcanoes near the North Pole. Data obtained with the Planetary Fourier Spectrometer (PFS) also indicates that short-lived methane gas has been discovered and its concentrations mapped in the Martian atmosphere above volcanic regions. This leads to the assumption that Mars may still be geologically active today, as the methane might be generated and introduced into the atmosphere by volcanic activity present underneath the surface of Mars.

On HRSC images of areas at low to mid-latitudes – close to the equator – surface features that can only have occurred as a result of the action of glacial ice are recognisable. Evidence indicates three episodes of activity in the last 300 million years, the most recent of which may have taken place just four million years ago. An ice age at mid-latitudes is impossible in today’s climatic conditions. Hence scientists presume that dramatic climatic changes must have occurred on Mars, since the inclination of Mars’ rotational axis has undergone major fluctuations. This means that different climatic conditions might have been predominant at the equator and in other regions of Mars at other times.

Mars: A dry, rocky river bed, in the shape of a narrow channel, lying in a larger valley in the Libya Montes highland region. The elevation is exaggerated by a factor of three (view looking northeast).
Mars: A dry, rocky river bed. Credit: SA/DLR/FU Berlin (G. Neukum).

Data from the MARSIS (Mars Advanced Radar for Subsurface and Ionosphere Sounding) radar sounder shows that layered sediments at the Martian North Pole consist of almost pure water ice. Meanwhile the OMEGA spectrometer has produced maps of water and methane ice deposits. Observations by Mars Express have proven that much more water exists beneath the surface of Mars in the form of ice, as was anticipated ten years ago.

The data obtained with ASPERA (Energetic Neutral Atoms Analyser) show that the solar wind penetrates deeper into the Martian atmosphere than was previously assumed (down to 250 kilometres). The loss of energetic ions as a result of this is relatively low. The loss of atmospheric constituents occurs in episodic ‘outbursts’, the cause of which is not yet understood. In the absence of a magnetic field, protons and helium ions in the solar wind penetrate the Martian ionosphere to a depth of 270 kilometres and cause planetary oxygen ions to be accelerated by the energy-rich particles and flow outwards. This occurs at lower altitudes and also with greater efficiency than was previously thought.

For the first time, clouds of methane ice have been discovered, investigated and imaged in the Martian mesosphere using the HRSC, OMEGA, PFS (Planetary Fourier Spectrometer) and SPICAM (Ultraviolet and Infrared Atmospheric Spectrometer) instruments.

The mission has also yielded a wealth of research results; particularly concerning the Martian moon Phobos. These results include the most accurate determination of its mass, its exact path and its volume and density, as well as the discovery of backscattered solar wind protons by the ASPERA instrument. Furthermore, the sharpest images to date of this moon have been captured, with a resolution of 4 metres per pixel. Among other things, these seem to confirm that Phobos is orbiting Mars faster and faster and is slowly getting closer to the planet, before it potentially breaks up as a result of tidal forces in 10-20 million years, colliding with Mars.

Credit: SA/DLR/FU Berlin (G. Neukum).
Source URL: http://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10463/701_read-882/

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Helio Now

Solar Dynamics Observatory

Solar Dynamics Observatory 2017-08-17T09:49:00Z
Observatory: SDO
Instrument: AIA
Detector: AIA
Measurement: 171

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