When discussing Mars exploration, it is easy to forget that NASA, the US space agency is far from alone. Both Europe and India are currently operating vehicles in orbit around Mars, while in 2004, the European Space Agency became only the third agency in the world to attempt a landing on Mars, when the British built Beagle 2 mission separated from its Mars Express parent craft but unfortunately failed to safely arrive on the surface of Mars.
Mars Express has gone on to be one of the most successful Mars orbital mission on record, carrying out a range of duties similar to those of NASA’s Mars Reconnaissance Orbiter (MRO), which it preceded to Mars by some two years. Now approaching the end of its 12th year in operation around the planet, Mars Express continues to return a wealth of data to Earth and also functions as a back-up communications relay for the two NASA rovers currently operating on the surface of the Red Planet.
An artist’s impression of Beagle 2 on Mars (image: European Space Agency)
Quite what happened to Beagle 2 remained unknown until early in 2015. It had been thought the tiny lander, just 1 metre (39 inches) in diameter but packing a huge amount of science capabilities into it, had been lost as a result of burning up in Mars’ tenuous atmosphere or as a result of its parachute landing system or air bags failing. However, as I reported in January 2015, images captured by NASA’s MRO revealed Beagle 2 had landed quite safely, but one of its solar panels failed to deploy, preventing the craft from communicating with Mars Express and Earth.
In 2018, ESA, working in conjunction with the Russian Federal Space Agency, Roscosmos, plan to overcome Beagle 2’s failure to gather science from the surface of Mars with a rover vehicle called ExoMars Rover, part of an ambitious 2-phase mission itself entitled “ExoMars”, and which commences in 2016.
ESA’s ExoMars TGO: due for launch in March 2016, part of a 2-phase mission to search for direct evidence of life, past or present, on Mars. In this artist’s impression, the capsule-like Schiaparelli has already been detached from the circular base of the vehicle (image: European Space Agency)
The first part of the mission will commence in March 216 with the launch of the ExoMars Trace Gas Orbiter (TGO), a telecommunications relay orbiter and atmospheric gas analyser mission. This will arrive in orbit around Mars in December 2016 and will proceed to map the sources of methane on Mars, as well as analyse and study other trace gases. Methane is of particular interest to scientists its likely origin is either present-day microbial life existing somewhere under the surface of the planet, or the result of geological activity. Confirmation that either is the cause would be of significant scientific benefit.
Whilst in operation in Mars obit, TGO will deploy Schiaparelli, an Entry, Descent and Landing Demonstrator Module (EDLM). This is intended to test some of the key technologies needed to safety see a rover-carrying lander onto the surface of Mars, such as the ability to control touchdown orientation and velocity. Most uniquely, the landing will take place during the Martian dust storm season, presenting scientist with the opportunity to characterise a dust-loaded atmosphere during entry and descent, and to conduct surface measurements associated with a dust-rich environment.
The Advanced Prototype ExoMars Rover undergoing remote deployment testing in 2015 (image: European Space Agency)
The 2018 ExoMars Rover mission, although yet to be finalised, is primarily designed to find evidence of microbial life, past or present, under the Martian surface. It is provisionally scheduled for launch in May 2018, although this may be delayed until August 2020, around the time NASA Mars 2020 rover mission is due to fly.
The ExoMars vehicle is somewhat larger than NASA’s solar-powered Opportunity rover, but at some 207 kg (456 lb), is about one-third the mass of Curiosity and the Mars 2020 rover. A unique aspect to ExoMars Rover is that it will carry a drilling system aboard which, for the first time, will allow samples to be obtained from almost 2 metres (6.5 ft) below the surface of Mars. The rover is expected to operate for around 6-7 months, but could remain operational for much longer. During that time, it should cover a distance of around 4 km (2.5 mi), after landing in early 2019.
The four proposed landing sites for ExoMars Rover. The colours on the map represent the relative elevations of surface features on Mars. White / Red refer to the highest elevation, such as the Tharsis Bulge and the great volcanoes to the north-west, and blue the low-lying regions, such as the far northern latitudes and the great impact basin of Hellas in the south-east, which likely caused the Tharsis Bulge upwelling
In September I reported on images captured by the New Horizons space probe of the night side of Pluto, backlit by the distant Sun. In a follow-up to those images, the New Horizons team has released stunning high-resolution images captured by the probe shortly after passing the point of closest approach to Pluto on July 14th, 2015.
The images were captured from a distance of just 18,000 km (11,000 miles) from Pluto using the Multi-spectral Visible Imaging Camera (MVIC), part of New Horizon’s Ralph suite of instruments, which were pieced together to form a magnificent view of Pluto with a resolution of some 700 metres per pixel.
The mosaic of images shows the rich complexity of both Pluto’s surface features and its atmosphere, the enhanced images clearly bringing the bands of haze in the latter into sharp relief.
An enhanced image of Pluto’s night side, composed of images captured by the MVIC instrument on New Horizons on July 14th, 2015. As Pluto is “tipped over” on its axis by 120 degrees, the planet’s north pole is to the right and south pole to the left (image: NASA/JPL / JHUAPL / SwRI)
The clearest detail of Pluto’s surface can be seen to the right, which because the planet’s axis is tilted by 120-degrees, is the north polar region. The sheer ruggedness of the terrain can be seen here, some of the pitted hills almost looking like clouds above a distant landscape. However, the left side, and the south pole isn’t entirely without interest: caught by the glow of sunlight refracted by Pluto’s tenuous atmosphere, the rugged nature of the little world’s chaotic surface can also be seen.
Subject to enhancement, a portion of the images capturing the northern regions of Pluto reveal even more detail, particularly within the complex layering of Pluto’s atmosphere, where the enhancements reveal it to be made up of around a dozen layers, far more than had been thought during New Horizon’s final approach to Pluto in late June. These layers are made up of tholins, soot-like organic compounds created as a result of ultraviolet radiation from the sun interacting with the upper layers of Pluto’s atmosphere. These particles, undergoing some chemical changes as they drift back down through the various layers, eventually precipitate down onto Pluto’s surface, staining it red.
An enhanced image of Pluto north polar region revealing an incredibly complex surface of hills and valleys, ice features and high mountains, while above can be seen an enhanced view of the complex atmospheric banding (image: NASA/JPL / JHUAPL / SwRI)
Cassini’s Enceladus Encounter
Cassini, NASA’s deep space probe exploring Saturn and his retinue of moons as a part of the Cassini-Huygens mission, is approaching the end of its 20-year mission. Launched in 1997, and following a 7-years transit to Saturn, Cassini has been studying the system in great detail, and delivered a tiny European lander vehicle, Huygens, to the surface of Titan, the largest moon in the solar system, and one with its own rich atmosphere, and standing bodies of liquid on its surface.
With fuel reserves set to expire in late 2017, Cassini will be ordered to fly into Saturn’s own dense atmosphere before it does so, where it will burn-up. In the meantime, however, the vehicle continues to return a marvellous wealth of data about the Saturn system, including several studies of another of the giant planet’s remarkable moons, Enceladus.
Enceladus revealed: captured on October 28th, this image reveals the icy beauty of the moon as Cassini closes for its penultimate, and closest, approach (image: NASA/JPL / Space Science Institute)
Like Jupiter’s moon Europa, Enceladus is a domain of ice, under which likely sits an ocean of liquid water. Shortly after arriving in orbit around Saturn, Cassini made the first of numerous flybys of the little Moon, which is just 500 km (310 mi) across, and detected the presence of a very thin atmosphere primarily made up of water vapour. In particular, the craft observed geysers erupting from the south pole, spewing water vapour, ice particles and other material into space, some of which likely contributes to Saturn’s “E” ring.
At the end of October 2015, Cassini made its penultimate flyby of Enceladus, passing over the Moon at an altitude of just 48 km (30 mi) and at a speed of some 30,000 kph (19,000 mph), diving through another of the geyser plumes in the process to measure the composition of gas and ice particles launched from the underground ocean.
A stunning images taken by Cassini following the October flyby reveals a crescent Enceladus floating above Saturn’s magnificent rings (image: NASA/JPL / Space Science Institute)
In particular, the Cassini science team will be analysing the data returned by Cassini following the flyby to see if the sensors found any evidence of molecular hydrogen in the plumes. Doing so would help verify suspected hydrothermal activity is taking place on the floor of Enceladus’ ice-shrouded ocean which could give rise to hot environments rich in mineral and chemical deposits suitable for the development of microbial life, just as deep-ocean thermal vents here on Earth provide life-sustaining environments.
Cassini will make one more return to Enceladus on December 19th, but will pass further from the little Moon as its orbit gradually swings it around Saturn for a further and final set of encounters with giant Titan, before finally moving inwards to pass between Saturn and its rings for the first time to study Saturn’s atmosphere in detail as the mission draws to a close in 2017.
Dawn Descends Over Ceres
On October 23rd, the NASA / ESA joint mission to explore two of the solar system’s three “protoplanets” located in the asteroid belt between the orbits of Mars and Jupiter, commenced manoeuvres to lower itself to is final orbit around Ceres.
The Dawn spacecraft, which arrived at Ceres in March 2015, after a 2.5 year transit flight from Vesta, its first destination, fired its ion engine to start reducing its orbit from 1,450 kilometres (915 miles) to just 380 km (235 mi), a manoeuvre which should see the vehicle spiral gently downwards to arrive in its new orbit in mid-December. At that time, Dawn will commence a final mapping and data-gathering mission, providing images with a resolution of 35 metres (120 ft) per pixel.
Occator crater and its bright spots images from directly overhead and a distance of 1,450 km (915 miles) by the Dawn space vehicle (image: NASA / JPL / DLR)
It is hoped that this final science orbit will offer definitive data on precisely what is giving rise to a series of odd bright spots within the crater Occator on Ceres, and which appear to be related to what seems to be a small and very localised trace atmosphere within the crater. Current thinking is the bright markings are salt or ice water deposits which are being out-gassed from Ceres’ interior.
Britain’s Spaceplane Gets £80 million Investment
SABRE is the name of a radical “air-breathing” hybrid engine which has been in development by a small British company called Reaction Engines Limited (REL) since the late 1990s. The aim is to reduce the amount of on-board oxidiser required in the rocket combustion process by allowing the engine to draw on the air around it during the initial ascent through the denser part of the Earth’s atmosphere, much like a regular jet engine uses the air around it. Only when the air becomes too thin to support combustion does the rocket engine switch over to its on-board supplies of liquid oxygen to burn with its liquid hydrogen fuel.
Ultimately, REL hope to use the SABRE engine in a single stage to orbit (SSTO) vehicle called Skylon, a fully reusable space launch vehicle, capable of operating from and to a conventional runway just like an aeroplane, and carrying up to tonnes into low Earth orbit. However, the SABRE engine potentially has a wide range of applications, including a purely “air-breathing” variant (called Scimitar) which could be used to power aircraft within Earth’s atmosphere at speeds close to five times that of sound.
REL propose using the SABRE engine in their Skylon spaceplane capable of lifting up to 15 tonnes (cargo or 24 passengers) into orbit. however, the engine has many potential uses, hence the interest from BASE Systems and the UK government (image: REL)
On Monday, November 2nd, REL announced that BAE Systems Ltd is to invest some £20.6 million (US $31.8 million) in REL in return for a 20% stake in the company, while the UK government has awarded a further £60 million (US $92.8 million). Together with recent funding from the EU, REL has now raised some £95 million (US $146.6 million) to further develop SABRE.
Skulls in the Sky
Halloween 2015 brought with it a creepy-looking visitor which looked down on Earth as many across the world took to marking All Hallows Eve on Saturday, October 31st.
The visitor in question was asteroid 2015 TB145, a lump of rock around 600 metres (1,968 feet) across. Tumbling through space, it passed by the Earth at a distance of roughly 480,000 km (300,000 miles) – slightly further from us than the orbit of the Moon, at a speed of some 126,000 kph (78,293 mph).
Such Earth-passing asteroids are not rare, although this one was only identified on October 10th, 2015. It well be the last close passage to Earth by a very large asteroid until 2027, and its size offered scientists a unique opportunity to image it using radar.
Asteroid 2015 TB145 in an eerily skull-like image captured by the Arecibo Observatory on Friday, October 30th, 2015.
On Friday, October 30th, the The Arecibo Observatory in Puerto Rico used radar mapping to capture an image of the asteroid in which it looks like a gigantic skull. It was all an optical illusion of course, the combined result of the radio reflections from the asteroid giving rise to the grey shaded image and the effect of pareidolia, in which the human brain perceives shapes and patterns that aren’t really there; as the asteroid tumbled through space, the similarities to a human skull were quickly lost as the radar reflections changed.
Nevertheless, it was fittingly spooky for Halloween!
Discover Gale Crater
I’ve written extensively about NASA’s Curiosity rover and its explorations within Gale Crater on Mars since its arrival there in August 2012. Now NASA and the Los Angeles Times have combined to provide a virtual reality exploration of Gale Crater, which examines some of the principal features to be found there, traces the rover’s route from crater floor and up the flank of “Mount Sharp” and which allows visitors to fly over the crater or take a guided tour using simple keyboard controls.
The Curiosity rover team have released a further study showing that ancient Mars was capable of storing water in lakes over an extended period of time, and that this water was a principal component in the creation of “Mount Sharp”, the mound at the centre of Gale Crater, currently being investigated by the NASA rover.
This forms the latest in a series of reports on the subject of water on Mars and in Gale Crater to be published by the Curiosity science team, and comes almost a year after I wrote about studies released by the team which detailed how “Mount Sharp” – more formally known as Aeolis Mons – was most likely formed by sediments laid down by successive wet period in Mars’ ancient past.
“Observations from the rover suggest that a series of long-lived streams and lakes existed at some point between about 3.8 to 3.3 billion years ago, delivering sediment that slowly built up the lower layers of Mount Sharp,” said Ashwin Vasavada, Mars Science Laboratory project scientist, discussing the new report.
In December 2014, NASA issued a report on how “Mount Sharp” was likely formed. On the left, the repeated depositing of alluvial and wind-blown matter (light brown) around a series of central lakes which formed in Gale Crater, where material was deposited by water and more heavily compressed due the weight of successive lakes (dark brown). On the right, once the water had fully receded / vanished from the crater, wind action took hold, eroding the original alluvial / windblown deposits around the “dry” perimeter of the crater more rapidly than the densely compacted mudstone layers of the successive lake beds, thus forming “Mount Sharp”
However, until Curiosity actually started studying “Mount Sharp” in detail, the accuracy of the earlier studies couldn’t be completely verified. The latest results from the rover indicate that these wetter scenarios were correct for the lower portions of Mount Sharp, and that the filling of at least the bottom layers of the mountain occurred over a period of less than 500 million years, mostly as a result of material deposited by ancient rivers and lakes.
The new report also comes on top of confirmation that the recurring slope lineae (RSL) features seen on Mars from orbit are most likely the result of outflows of water which are occurring today. together they are reshaping some of the thinking around water on Mars – and what might have happened to it.
“What we thought we knew about water on Mars is constantly being put to the test,” said Michael Meyer, lead scientist for NASA’s Mars Exploration Programme. “It’s clear that the Mars of billions of years ago more closely resembled Earth than it does today. Our challenge is to figure out how this more clement Mars was even possible, and what happened to that wetter Mars.”
Curiosity has found plenty of evidence for water on the floor of Gale Crater, which likely took the form of one or more lakes during the wetter parts of Mars’ history, before becoming rivers and streams later. Strata at the foot of “mount Sharp” (shown above) strongly suggested water played a significant part in forming the mound, and the evidence for this being the case has continued to be revealed as the rover climbs the lower slopes
Currently, images of the flanks of the mound returned by the rover and from orbit suggest water-transported sedimentary deposition may have extended at least 150 to 200 metres (500 to 650 feet) above the crater floor, and possibly as high as 800 metres (approx 1/2 a mile). This both indicates that there was at least one standing body of water in the crater and further confirms that “Mount Sharp” was a direct result of sediments deposited by this water. Or at least, the lower slopes were; there is currently little evidence for the sedimentary strata extending about the 800 metre mark, however. This has led to speculation that wind-blown deposits are responsible for the upper reaches of the mound.
Taken together, the recent findings concerning Mars and its water suggest that the planet’s history is far more complex than had been thought. “We have tended to think of Mars as being simple,” John Grotzinger, the former project scientist for the Curiosity mission said of the latest findings.
“We once thought of the Earth as being simple too,” he continued. “But the more you look into it, questions come up because you’re beginning to fathom the real complexity of what we see on Mars. This is a good time to go back to re-evaluate all our assumptions. Something is missing somewhere.”
Pluto’s Water
The blue haze of Pluto’s atmosphere: released on October 8th, this true colour image taken after the New Horizons spacecraft had completed its closest approach to the dwarf planet shows Pluto’s night side ringed by the blue haze of its thin atmosphere, as illuminated by the distant Sun, far away on the other side of the little world
The latest images and data to be received on Earth from NASA’s New Horizons space vehicle reveal Pluto’s atmosphere to be a rich blue in colour, and confirm that water ice exists on theplanet.
“Who would have expected a blue sky in the Kuiper Belt? It’s gorgeous,” said Alan Stern, New Horizons principal investigator as the striking image shown above was released as part of the latest batch of pictures and data to be received from the space craft and undergo processing and initial analysis.
The blue colour indicates that the haze within Pluto’s atmosphere is made up of a lot very fine of particulate matter, which scatters blue light from the Sun more easily than other colours, due to blue having a shorter wavelength (which is also the reason the sky we see here on Earth also appears blue, because that wavelength is easily scattered by the tiny particles making up our atmosphere).
In Pluto’s case, it’s thought that the particles in the atmosphere are largely tholins, created by ultraviolet radiation from the Sun breaking down the methane and nitrogen in Pluto’s upper atmosphere, allowing their molecules to gradually recombine into the more complex tholins, which draft down through the atmosphere, undergoing further changes, before eventually reaching the surface of the planet, giving it a distinctive reddish colour.
Instruments forming the Ralph suite aboard New Horizons have identified regions of exposed water ice on Pluto which occur in regions which have corresponding deposits of tholins. Quite what the relationship is between the two is unclear. The water ice deposits are shown in blue on the inset image simply for convenience, and not because that’s how they appear on Pluto
The discovery of water ice on Pluto has taken scientists by surprise. Not so much because it is there, but because it appears to be somehow related to areas of heavy tholin deposits. Confirmation of the presence of water ice came from data returned by the Ralph instrument suite aboard New Horizons, but just how widespread it might be isn’t clear, as it seems that it might be masked elsewhere by other surface material.
A lunar eclipse “blood moon” seen Idaho, December 2011 (image: Matt Mills / Reuters)
The night of Sunday 27th / Monday 28th September promises a very special astronomical event for those fortunate enough to have clear skies overhead and are willing to stay up late (in the UK and Europe). It will see a total lunar eclipse take place at the time when the Moon reaches perigee, its closest approach to Earth in its orbit and giving rise to both a so-called “supermoon” and a “Blood Moon”.
A “supermoon” occurs when a full moon coincides with the time when the Moon is nearing its minimum distance to Earth, a distance of roughly 363,000 kilometres (226,875 miles), leading to it appearing 7-8% larger than when seen as a full Moon at other points in its orbit. A “blood moon” is the result of the Earth’s atmosphere, lying between the Sun and Moon, scatter blue light more strongly than red, so the latter reaches the Moon more strongly, giving it a reddish-brown colour when seen from Earth.
A total lunar eclipse occurs when the Sun, Earth and Moon are lined up so that the Earth is between the Sun and Moon, and the latter sits within the Earth’s shadow (image: NASA)
Lunar eclipses are not that rare – this one will be the second of 2015, for example. However, “supermoons” are somewhat rarer. The last was in 1982, and the next will not be until 2033. So, if you want to see a really big blood moon, and you live in Western Europe, West Africa, the Eastern side of the USA and Canada or south America, then the 27th / 28th September is the night to do so. People further afield – eastern Asia, the middle east, eastern Europe and the western sides of Canada, the USA and South America will see a partial eclipse.
In the UK, the period of eclipse will start at around 01:00 BST (00:00 GMT) on the morning of Monday, 28th September, and run through until around 05:00 BST (04:00 GMT). That’s from 20:00 through to around 01:00 EDT in the USA / Canada, and 02:00 through 06:00 CET in Europe).
A total lunar eclipse and the gradual change in the Moon’s colour as seen from Earth which sees total lunar eclipses sometimes referred to as “blood moons” – the result of sunlight passing through the Earth’s atmosphere and striking the Moon’s surface (animation: Wikipedia)
The eclipse brings to a close what is referred to as a “tetrad” of total lunar eclipses – that is, four occurring “back-to-back”, with no partial eclipses between them, the first of which occurred in April 2014 and the “middle two” in October 2014 and April 2015. Some have a misguided view that this “tetrad” as being of particular significance because such events are “rare”, and this particular one started on the Passover.
However, while there can be long periods of time between occurrences of tetrads, they can also pop-up relatively frequently. For example, this century will see a total of nine tetrads occur, the first having taken place in 2003/4. Nor is the fact that this particular series started on the Passover particularly unusual; there have been eight tetrads so far coinciding with Passover since the first century AD.
So, if you are in a position to see the eclipse, you can leave the tinfoil hat on the table and step outside quite safely. Totality should occur around two hours after the eclipse starts (e.g. 03:00 BST in the UK / 04:00 CET, 22:00 EDT on the 27th September), and that’s the best time to enjoy the blood moon in all its glory.
The eclipse will also give NASA the chance to measure the full range of temperature variations during such an event. This will be done by the Lunar Reconnaissance Orbiter (LRO), a solar-power vehicle which has been observing the Moon since 2009.
Normally during an eclipse, the LRO has most of its systems powered down to reduce the load placed on the battery systems. However, mission controllers are confident they will be able to run an instrument which will allow it to accurately measure the amount of heat loss the surface of the Moon experiences when inside the Earth’s shadow, further helping them to understand the composition of the Moon’s regolith and its function as an insulator.
NASA and the Applied Physics Laboratory (APL) at John Hopkins University kept their promise a little earlier than expected.
With the resumption of image and data transmissions from New Horizons, at the start of September, they had indicated that Fridays would henceforth, and for the course of the next 12 months, be known as Pluto Friday, the day on which the latest raw images from the mission to that distant tiny world and its companions would be released.
However, the first set of images came a little sooner than advertised: on Thursday, September 10th, and they continue to show two tiny worlds which continue to astound and have planetary scientists rethinking much about their understanding of dwarf planets.
“Pluto is showing us a diversity of landforms and complexity of process that rival anything we’ve seen in the solar system,” New Horizons’ principal investigator Alan Stern, from the Southwest Research Institute in Colorado, said in a statement. “If an artist had painted this Pluto before our flyby, I probably would have called it over the top — but that’s what is actually there.”
Charon, Pluto’s largest companion, as seen by New Horizons on July 14th, 2015, from a distance of some 464,000 kilometres (290,000 miles), revealing a rich and diverse range of surface features (image: NASA / JHU / APL / SWU) – click any image for the full-size version
The images render details as small as 400 metres / 440 yards per pixel on the surface of Pluto, and reveal features that have scientists agog with excitement; so much so that at a NASA press conference, the images were summarised thus, “it’s complicated!”
In them, we can see a rich complexity of features: nitrogen ice flows which have apparently oozed (and might still be slowly oozing) out of mountain ranges and across broad plains; mountain ranges which are themselves reminiscent of chaotic regions on Mars and Jupiter’s Europa; complex valley systems which might have been carved by the action of material flowing across the planet; and even – perhaps most curiously of all – what seem to be wind-blown fields of dunes.
A synthetic perspective view of Pluto, based on the latest high-res received from New Horizons presents a view of Pluto from around 1,800 km (1,100 mi) above Pluto’s equatorial area. Towards the bottom of the image is the cratered and dark region dubbed “Cthulhu Regio”, and above it, the bright “heart” of Pluto, the “Tombaugh Regio”, with the icy plains of “Sputnik Planum” prominent. The images used to create this view were captured from a distance of 80,000 km (50,000 mi) from Pluto (images: NASA / JHU / APL / SWU) – click any image for the full-size version
What is also particularly striking about these images of Pluto is the way that they reveal some of the oldest (geologically speaking) regions yet seen on the planet sitting right alongside what are the youngest locations on the planet, adding further emphasis to the idea that Pluto has been, and might still be, an active world.
But what about those dunes mentioned above? If they are indeed what the images released on September 10th suggest, Pluto has once again served up a surprise.
“Seeing dunes on Pluto, if that is what they are would be completely wild!” William McKinnon from the mission’s Geology, Geophysics and Imaging (GGI) team, said, “because Pluto’s atmosphere today is so thin. So either Pluto had a thicker atmosphere in the past, or some process we haven’t figured out is at work. It’s a head-scratcher!”
The dunes of Pluto? This image, representing a portion of Pluto’s surface some 350 km (220 mi) across, shows some of the planet’s older, chaotic terrain at the bottom, and an enigmatic field of dark, aligned ridges that resemble dunes toward the top. The image was captured from a distance of 80,000 km (50,000 mi) from Pluto (images: NASA / JHU / APL / SWU)
More is also being discovered about Pluto’s atmosphere, which is also proving to be a lot more complex than had originally been thought, having many more layers within its thin haze than had been thought. However, these layers of haze have allowed the science team to glimpse surface features which might otherwise have remained unseen as sunlight caught by the haze over the terminator – the divide between the day and night sides of the planet – cast a soft glow over part of Pluto’s night side. When enhanced through careful processing, this glow could be used to reveal what lay below.
It’s been a little quiet on the new images front where the New Horizons mission is concerned. The spacecraft, which performed the first ever flyby of Pluto and Charon in July, gathered a wealth of data, around 95% of which has remained aboard the spacecraft awaiting transmission back to Earth.
There have been a number of reasons this has been the case. First off, for the period following the close encounter, New Horizons continued to gather data and images of the Pluto-Charon system. Such is the design of the vehicle that while doing this, it couldn’t actually transmit information back to Earth. Also, once the data had been gathered it required sorting and prioritising ready for transmission back to Earth, and this again took time to do.
However, on Saturday, September 5th, New Horizons oriented itself to make contact with the Deep Space Network (DSN) operated by NASA for what was the start of a year-long “intensive” download of the 10 gigabits of data gathered by the craft, starting with information the science team regard as the highest priority data sets.
The reason the transfer will take so long is not only because the enormous distance between New Horizons and Earth, which takes radio signals moving at the speed of light over 4.5 hours to cross (a time which is slowly increasing), but also because the rate at which the data can be transmitted is limited.
Currently, the nuclear “battery” powering New Horizons can only produce around 2-10 watts of electrical power, which has to keep all of the various electrical systems warm and running. So to conserve power, the vehicle only transmits data at between 2-4 kbps. To put that in perspective, it would take you about 2 hours to download a single photo from your cellphone to your computer at those speeds.
NASA Deep Space Network (DSN) is a set of three communications facilities operated by NASA in Spain, Australia (shown above) and California. They are tasked with maintaining communications with NASA’s deep space and planetary missions. Located roughly 120-degrees apart around the Earth, the three facilities can between them maintain a constant radio observation on any spacecraft under their command as the Earth rotates.
Discussing the start of the extended data download from New Horizons, Alan Stern, the mission’s Principal Investigator, said, “this is what we came for – these images, spectra and other data types that are going to help us understand the origin and the evolution of the Pluto system for the first time.”
He continued, “and what’s coming is not just the remaining 95 percent of the data that’s still aboard the spacecraft – it’s the best datasets, the highest-resolution images and spectra, the most important atmospheric datasets, and more. It’s a treasure trove.”
To mark the receipt of data and images, NASA / JPL and John Hopkins’ APL have designated Friday as Pluto Friday, when they’ll be publishing that latest images, unprocessed, received from the spacecraft the previous week. The images will be available on the LORRI image catalogue, operated by JHU / APL, starting on Friday, September 11th, 2015.
In the meantime, here’s an animated video from NASA, showing the Pluto flyby, just to whet appetites.
Mars’ Atmosphere: Where did It Go?
One of the many mysteries of Mars is what happened to its atmosphere. All of the evidence gathered over the years about the Red Planet is that it once had an atmosphere dense enough to support free-flowing liquid water, and that potentially as much of 20% of the planet’s surface may have been submerged.
So what happened? There are a number of theories. One of these is that over time, the action of the solar wind, combined with Mars’ relatively weak gravity, effectively “scooped” much of the atmosphere away into space. Measurements of heavy and light carbon ratios in the present day atmosphere lend considerable weight to this theory.
An artist’s impression of what a wet Mars may have looked like, based on the ratio of deuterium contained within the Martian polar caps
Another idea is that carbon dioxide, the major constituent of Mars’ atmosphere may have been “sequestered” – that is, “pulled” out of the atmosphere to be stored in rocks and subsurface deposits by various chemical reactions, forming carbonate minerals in the process.
This theory was given its own boost when a region of Mars called Nili Fossae, approximately as big as the US state of Arizona, was found to have huge deposits of carbonates (more recently this region has been of interest to scientists due to the discovery of impact glass, helping to mark the region as a candidate target for the Mars 2020 rover mission).
Inara Pey: Living in a Modemworld