Space Sunday: mesas, dunes NEOs, comets and launches

A dramatic look back: in the foreground is the lower slope of one of the "Murray Buttes", in the far distance the tall peaks of Gale Crater's huge rim. One of the final images taken by Curiosity from within the region of the buttes on Thursday, September 8th, the rover's 1,454 sol on Mars. Credit: NASA/JPL / MSSS

A dramatic look back: in the foreground is the lower slope of one of the “Murray Buttes”, in the far distance the tall peaks of Gale Crater’s huge rim. One of a series of images taken by NASA’s Curiosity rover on Thursday, September 8th, the rover’s 1,454 sol on Mars. Credit: NASA/JPL / MSSS

NASA’s Mars Science Laboratory rover, Curiosity, has said “farewell” to “Murray Buttes” in a stunning series of images, as it continues its climb up the slopes of “Mount Sharp”, a massive mound of deposited material located at the central impact peak of Gale Crater.

The mesas of “Murray Buttes” mark the upper extend of the transitional “Murray Formation”, where the material deposited during the earliest centuries of “Mount Sharp’s” formation merge with the rock comprising the crater floor. Curiosity has been passing by the area of the buttes for a little over a month now, carrying out examinations of the rock surface and gathering samples of mudstone for analysis.

Murray Buttes with the faint outlines of Gale Crater beyond, as images on Thursday, September 8th 2016, by NASA's Curiosity rover during its 1m454 sol on Mars. Credit: NASA/JPL / MSSS

“Murray Buttes” with the faint outlines of Gale Crater beyond, as images on Thursday, September 8th 2016, by NASA’s Curiosity rover during its 1,454 sol on Mars. Credit: NASA/JPL / MSSS

Believed to be the eroded remnants of ancient sandstone that originated when winds deposited sand after lower “Mount Sharp” had formed, the buttes rival anything of a similar nature found on Earth in terms of dramatic looks and structure. So much so that while we’re hardly likely to see Clint Eastwood ride his horse around the base of one, they would nevertheless fit neatly into a Sergio Leone western.

Several of the pictures – mosaics of images captured by the rover which have been white-balanced to match typical Earth daylight lighting conditions and then stitched together to offer complete scenes – reveal the deeply layered nature of the sandstone, sandwiched in what is referred to as “cross-bedding”. This indicates that the formations are the result of both wind deposition of material and then wind erosion, further confirming the idea that “Mount Sharp” was initially formed as a formed as a result of Gale Crater once being home to a great lake, before the waters receded and wind action took over.

A closer view of the layered nature of the sandstone deposits forming "Murray Buttes", showing the "cross bedding" of the layers, indicative of the role that wind played in their deposition / formation. This picture comprises a mosaic of images captured by Curiosity rover on Thursday, September 8th, 2016 during its 1,454 sol on Mars. Credit: NASA/JPL / MSSS

A closer view of the layered nature of the sandstone deposits forming “Murray Buttes”, showing the “cross bedding” of the layers, indicative of the role that wind played in their deposition / formation. This picture comprises a mosaic of images captured by Curiosity rover on Thursday, September 8th, 2016 during its 1,454 sol on Mars. Credit: NASA/JPL / MSSS

The images were taken as Curiosity traversed the base of the final butte, where it gathered a final drilling sample on September 9th. On completion of the sample-gathering, the rover will continue farther south and higher up Mount Sharp, leaving these spectacular formations behind.

Curiosity's route up the slopes of "Mount Sharp". Credit: T.Reyes / NASA/JPL

Curiosity’s route up the slopes of “Mount Sharp” – click for full size. Credit: T.Reyes / NASA/JPL

The Sand Dunes of Shangri-La

On September 7th, NASA issued a video showing the latest radar images captured by the Cassini probe of the surface of Saturn’s largest moon, mighty Titan. The data was gathered as the probe swept by the huge moon – which is blanketed by a thick atmosphere and is known to have lakes and rivers of liquid hydrocarbons on its surface – at a distance of some 976 km (607 mi) on July 25th, 2016 – one of the closest passes over the moon the vehicle has ever made.

Because of the moon’s thick atmosphere, conventional camera systems cannot be used to probe Titan’s mysteries, so Cassini uses a radar system to “map” surface features in black-and-white. Of particular interest to mission scientists during the July 25th flyby was a dark patch along Titan’s equator, previously images by the radar system at much greater distances and dubbed “Shangri-La”. And area which revealed itself to be – in part – a region of linear dunes, mostly likely comprised of grains derived from hydrocarbons that have settled out of Titan’s atmosphere, and which have been sculpted by Titan’s surface winds. Scientists can use the dunes to learn about winds, the sands they’re composed of, and highs and lows in the landscape.

Also captured by the radar is an arena dubbed “Xanadu annex”, believed to be an out-thrust of chaotic terrain from a region dubbed “Xanadu” just to the north of “Shangri-La”. First imaged by the Hubble Space Telescope in 1994, just before the Cassini / Huygens mission was launched, “Xanadu” and its annex are thought to be remnants of the moon’s icy crust before it was covered by organic sediments from the atmosphere.

OSIRIS-REx Lifts-off as an Asteroid Sweep By Earth

On Thursday, September 8th, NASA successfully launched OSIRIS-REx on a 7-year trek to reach asteroid Bennu, where it will gather surface samples and return them to Earth for analysis. The mission, which I previewed in my last Space Sunday report, lifted-off flawlessly from Space Launch Complex 41 at Cape Canaveral Air Force Station at 19:05 EDT, atop its Atlas V booster at the start of a journey which will carry it a total of 7.2 billion kilometres (4.5 billion miles).

The Atlas V booster carrying OSIRIS-REx shortly after lift-off on Thursday, September 8th. Credit: Ken Kremer

The Atlas V booster carrying OSIRIS-REx shortly after lift-off on Thursday, September 8th. Credit: Ken Kremer

Witnessing the launch was principal investigator Dante Lauretta, from the University of Arizona. “I can’t tell you how thrilled I was this evening, thinking of the people who played a part in this,” he said following the launch.

“This represents the hopes and dreams and blood, sweat and tears of thousands of people who have been working on this for years.”

The mission will gather samples from the surface of the asteroid – a remnant from the formation of the solar system – and will also map Bennu’s orbit around the Sun and the influences affecting it.

This is because the asteroid is a near-Earth object (NEO): an asteroid which periodically passes across Earth’s orbit around the Sun, and can come very close to our planet whilst doing so. So close, in fact, that some estimates of Bennu’s future orbit suggest it will collide with Earth towards the end of the next century.

Nor is the risk of impact by Bennu a rare one. NEOs are actually surprisingly common. The first was identified in 1898, and between then and the end of the 20th century, the number slowly increased to around the 500+ mark. However in 2006, the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) commenced a systematic sky survey, and has clocked-up over 10,000 NEOs orbiting the Sun and which intersect Earth’s orbit.

Not all of them constitute a threat; anything coming within 45 million km (28 million mi) is classified as a NEO, but it takes a particular set of orbital mechanics for them to become a specific risk to Earth – and even then, not all of them are large enough to survive entry into our atmosphere. However, the number of NEOs is still climbing as observations continue, and estimates suggest there could be between 100,000 and a million objects varying in size from a few kilometres across to just a handful or metres, all periodically crossing Earth’s orbit. So the threat of something being out there which could strike our planet is a real one.

An animation of asteroid 2016 RB1 from images obtained by the Virtual Telescope Project on September 6, 2016. Credit: Gianluca Masi/Virtual Telescope Project.

An animation of asteroid 2016 RB1 from images obtained by the Virtual Telescope Project on September 6, 2016. Credit: Gianluca Masi/Virtual Telescope Project.

Almost to underline this, just a day prior to the launch of OSIRIS-REx, a very small asteroid swept past Earth at a distance of just 38,463 km (23,900 mi). To put that in perspective, it is roughly  one tenth of the distance between the Earth and the Moon, and just beyond the geosynchronous orbit used by communications satellites. Dubbed 2016 RB1, the little chunk of rock was estimated to be around 17m (56ft) across (compared to Bennu’s  492m / 1,614 ft) diameter). That’s roughly equivalent to the Chelyabinsk meteor that exploded over northern Russian on Friday, February 15th, 2013, recorded in the video below.

While too small to cause devastation – it would have disintegrated high up in the Earth’s atmosphere just like the Chelyabinsk object, 2016 RB1 was actually the third such object to scoot past the Earth in as many days. On September 2nd, asteroids 2016 RR1  and 2016 RS1 passed by at 0.32 and 0.48 lunar distance respectively, and each was also spotted just days before they zapped by. Which all goes to show that while space may be really big and mostly filled with a lot of “nothing”, those bits which do have “something” in them can be very busy places.

VSS Unity Completes First Captive-Carry Flight

It’s been a long road, getting from there to here.
It’s been a long road, but their time is finally near.

So go the words (with a slight modification on my part) to the theme for the television series Star Trek Enterprise. I’ve modified it slight, because the words could equally apply to Virgin Galactic, which is, among multiple space activities, attempting to establish the world’s first sub-orbital space tourism business.

VSS Unity, mated to the VMS Eve, is rolled from the Virgin Galactic hanger in the Mojave Desert, Thursday, September 8th, in preparation for its maiden captive-carry flight. Credit: Virgin Galactic

VSS Unity, mated to the VMS Eve, is rolled from the Virgin Galactic hanger in the Mojave Desert, Thursday, September 8th, in preparation for its maiden captive-carry flight. Credit: Virgin Galactic

In 2014, the company suffered the tragic loss of their first passenger-carrying vehicle, the VSS Enterprise, when co-pilot Michael Alsbury accidentally activated the vehicle’s “feathering” system at the wrong time. Intended to ease the craft back into the denser parts of the Earth’s atmosphere, Alsbury’s deployment of the system led to the spaceplane’s immediate break-up, killing him and leaving pilot Peter Siebold seriously injured.

Since then, Virgin Galactic have been working hard to get the programme back on course, and on September 8th, 2016 – the very day of Star Trek’s 50th anniversary – their new spaceplane, the VSS Unity, took to the air for the first time, slung beneath the Virgin Mother Ship Eve in what is called a captive-carry flight. Lasting a little under 4 hours, the flight allowed the spaceplane’s on-board systems to be tested as it was carried up to 15,00 metres (50,000ft) altitude, where it would be released to fly into space during an actual flight, before bringing it safely down to the ground.

Outwardly identical to the VSS Enterprise, the Unity is in fact an entirely new craft, built directly by Virgin Galactic rather than Scaled Composites, the company responsible for the Enterprise, and incorporating new propulsion, flight and safety systems – including a failsafe to ensure Alsbury’s error in prematurely deploying the “feathering” system cannot be repeated.

Unity still has a fair way to go before commercial operations start, with this flight being the first in a whole series of captive and free flights. However, this flight marks a significant step forward once more for the company.

Philae Found

Philae, Europe’s little washing-machine sized lander which touched-down on comet 67P/Churyumov-Gerasimenko in November 2014, has been found. The tiny lander, which took an unexpected “bounce” in the comet’s weak gravity after the failure of the systems designed to anchor it in place at the moment of surface contact, was discovered while the mission team were examining a set of recent images of 67P/C-G taken by the still-orbiting Rosetta spacecraft.

Philae found: an images of Comet 67P/C-G's surface captured by the orbiting Rosetta vehicle reveals the lander caught in a cleft, as indicated by the inset enhancement. Credit: ESA / Rosetta NavCam – CC BY-SA IGO 3.0

Philae found: an images of Comet 67P/C-G’s surface captured by the orbiting Rosetta vehicle reveals the lander caught in a cleft, as indicated by the inset enhancement. Credit: ESA / Rosetta NavCam – CC BY-SA IGO 3.0

While Philae may not have landed where intended, it still managed to carry out most of its science objectives immediately after eventually coming to rest. However, images from its on-board camera revealed in was deep in the shadow of what appeared to be a cliff, and unable to obtain enough sunlight for its solar panels to recharge its batteries. Instead, it was ordered into a “sleep” mode in the hope that, as the comet continued towards and around the Sun, the lander would gain enough sunlight to recharge its power systems.

Which is exactly what happened when, in June 2015, the lander briefly re-established contact with Rosetta and Earth.  Sadly, it didn’t last; and in January 2016, the hunt for the lander was called off without positive evidence of its resting place being found – until now. Ironically, it was located while the mission team were examining images of the comet in preparation to de-orbit Rosetta at the end of September 2016 and have it land on 67P/C-G (which it is not actually designed to do) before the last of its fuel is expended. However, it is still an important find.

A further enhancement reveals Philae to be effectively "tipped over" within the cleft, further limiting its solar panels to sunlight, as the missions team had theorised. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

A further enhancement reveals Philae to be effectively “tipped over” within the cleft, further limiting its solar panels to sunlight, as the missions team had theorised. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Not only does it bring a proper sense of closure to the lander’s mission for those directly involved in it, discovering the lander’s resting place allows the science team to put Philae’s three days of science into proper context, potentially revealing more about the comet in the process.

China Preps Second Space Lab for Launch

Tiangong-2, mounted on the top of its Long March 2F launch vehicle, emerged from its vehicle assembly building at China's Jiuquan Space Centre on September 9th, en route to the launch pad for an anticipated September 15th lift-off

Tiangong-2, mounted on the top of its Long March 2F launch vehicle, emerged from its vehicle assembly building at China’s Jiuquan Space Centre on September 9th, en route to the launch pad for an anticipated September 15th lift-off. Credit: CCTV

China rolled-out a Long March 2F launch vehicle at their Jiuquan Satellite Launch Centre in the north-western province of Gansu on September 9th, 2016 in preparation for the launch of the Tiangong-2 (“Heavenly Palace 2”) orbital laboratory.

The space lab, protected in a payload shroud atop the rocket, is expected to launch on, or shortly after, September 15th, and will orbit the Earth at an altitude of some 393 km (246 mi) through until at least 2022.

It is the second phase of China’s goal to establish a permanently crewed space station in the early to mid 2020s. This work started in 2011 with the launch of the Tiangong-1 facility, which was briefly visited by two crews in 2012 and 2013. It will culminate in the on-orbit construction of a large space station, starting with the launch of the Tiangogn-3 module in 2022.

In the interim, and unlike the Tiangong-1 unit, which was a demonstration test-bed for orbital rendezvous and docking capabilities rather than any kind of space science facility, Tiangong-2 will be a functional orbital laboratory, carrying a range of payloads developed by the National Space Science Centre (NSSC) under the Chinese Academy of Sciences (CAS), with collaboration from the University of Geneva in Switzerland.

The first crew is expected to fly to the station in October aboard the Shenzhou 11 space vehicle, and remain there for 30 days. The station will also be visited by China’s automated cargo vehicle / refuelling unit, Tianzhou-1 in early 2017.

A model of Tiangong-2, which will be 14.4 metres (47 ft) in length, 4.2 metres (14 ft) in diameter and mass 20 tonnes, seen docked with a crewed Shenzhou ("Divine Craft") orbital vehicle on the left (Credit: unknown originating source)

A model of Tiangong-2, which will be 14.4 metres (47 ft) in length, 4.2 metres (14 ft) in diameter and mass 20 tonnes, seen docked with a crewed Shenzhou (“Divine Craft”) orbital vehicle on the left (Credit: unknown originating source)

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