Space Sunday: radiation, rings and pollution

Missions like Elon Musk’s hopes for Mars need good radiation protection for crews – and NASA is working to bring this about. Credit: SpaceX

I’ve written several times about the risk radiation poses to dee space missions; particularly Galactic Cosmic Rays (GCRs), the so-called “background radiation” left over from the big bang. As I’ve noted, while solar radiation – up to and including Solar Particle Events (SPEs or “solar storms”) can be reasonably well dealt with, on account of the particles being relatively low-energy – 13 centimetres (5 inches) of water or similar liquid – is pretty good protection against the primary radiation threat of SPEs, for example – GCRs are far harder to deal with.

However, there are materials which can block them. Again, I’ve written about Hydrogenated boron nitride nanotubes (BNNTs). These are something being developed by NASA’s Langley Flight Centre in Virginia; extremely flexible, they can be used in the construction of key elements of space vehicles – walls, floors, ceilings, for example – and can even be woven into a material used as a lining in space suits to protect astronauts.  Similarly, borated polyethylene – already used for radiation shielding in nuclear reactors aboard US naval vessels, medical vaults and linear accelerators, among other applications – offers a means to provide primary radiation protection within the structure of space vehicles.

However, these are only effective in stopping primary radiation damage – that is, damage cause by the direct impact of radiation on living cells. A far, far greater risk people in deep space will face is from so-called secondary radiation,  particularly in the case of GCRs.  simply put, when a GCR particle collides with another, it sends energetic neutrons, protons and other particles in all directions, which can collide with others. It’s like a bullet striking something and scattering shrapnel, potentially doing damage to a lot of cells if they strike a living body. The problem here is that the more material used to block the effects of primary radiation damage, the more the risk of secondary radiation damage is increased.

Materials such as BNNTS and borated polyethylene could be used for surface vehicles and equipment as well

This means that there is unlikely to be a single solution to the issue of radiation exposure on deep space missions such as to Mars. Which is why scientists aren’t looking for one. NASA, for example has been conducting research into technologies such as BNNTs and magnetic shielding for space vehicles for over a decade. The latter, if possible, would use a magnetic field around a space vehicle to protect the crew, much as Earth’s magnetic field protects us. The problem here is that such systems currently require huge amounts of electrical power and can add a significant amount of mass to a space vehicle.

Another avenue of research being investigated is the use of pharmaceuticals as possible radiation inhibitors. Drugs such as potassium iodide, diethylenetriamine pentaacietic acid (DTPA) and the dye known as “Prussian blue” have for decades been used to treat radiation sickness. The theory is now that they could be used as part of a preventative regime of preventative treatment for astronauts on deep space missions.

The whole subject of radiation protection has become a focus in light of NASA’s “new” directive to return humans to the Moon and also because of Elon Musk’s determination to send humans to Mars, possibly as early as the mid-2020s. Because of this, NASA has been highlighting its research into radiation exposure management of late, which also includes solar weather forecasting (to help warn crews in deep space about the risk of SPEs, etc.), and in looking at 20+ years of orbital operations aboard the shuttle ISS and Russia’s MIr space station. All of this is leaving some at NASA feeling very positive about efforts to send humans beyond Earth orbit, as Pat Troutman, the NASA Human Exploration Strategic Analysis Lead, stated in a NASA press statement on the matter:

Some people think that radiation will keep NASA from sending people to Mars, but that’s not the current situation. When we add the various mitigation techniques up, we are optimistic it will lead to a successful Mars mission with a healthy crew that will live a very long and productive life after they return to Earth.

Whether progress on all fronts will be sufficiently advanced to encompass something like Elon Musk’s aggressive approach to human missions to Mars remains to be seen. However, with the “new” directive for NASA to return humans to the Moon, there’s a good chance we’ll see some of the current initiatives in radiation protection bearing fruit in the next few years.

The Risk Posed by Tiangong 1

Tiangong 1 (“Heavenly Palace 1”), the first Chinese orbital facility has been creating some sensationalist headlines of late.  Launched in 2011, the facility saw two crews spend time aboard it, prior to it being run on an automated basis from 2013. On March 21st, 2016 the Chinese Manned Space Engineering Office announced that they had disabled the facility’s data service in preparation for shifting their focus to the (then) upcoming Tiangong 2 facility and in allowing Tiangong 1’s orbit to decay so it would burn-up re-entering the upper atmosphere.

Tiangong 1. Credit: CMSE

The time-frame from re-entry was predicted to be late 2017 / early 2018. However, around the time Tiangong 2 was launched the Chinese space agency admitted they’d lost attitude control of the laboratory, so they could no longer orient it as it orbits the Earth. As a result, the facility has been under scrutiny from Earth by individuals and groups monitoring the rate of its orbital decay.

One of these observers is astrophysicist Jonathan McDowell of Harvard university. In early October he released a statement which indicated that as a loss of attitude control, increased friction has resulted in a sharp decline in Tiangong 1’s altitude to the point where it had reached the point were atmospheric drag now could see the vehicle re-enter the Earth’s atmosphere in the next few months. He also noted – accurately – that some elements of the 8.5 tonne vehicle could survive re-entry and reach the surface of the Earth (something the Chinese have always noted).

Unfortunately, his report led to some sensationalist responses from portions of the media. For example, one UK media tabloid blasted: “Out-of-control space station to smash into Earth THIS MONTH…and it could hit ANYWHERE. … A MASSIVE space station is hurtling towards Earth!” (block capital their own, not mine); other newspapers also highlighted the upper-end of the risk posed by the vehicle’s re-entry.

Needless to say such reports wildly over-egg the situation. The reality is that Tiangong’s orbit carries it over vast swathes of ocean and large areas of sparsely populated land. As such, while there is a risk of parts of the station reaching the ground, the chances of them hitting a populated area are remote. In this, Tiangong reflects the US Skylab mission in 1979 and the Russian Salyut 7 / Cosmos 1686 combination of 1991. Both of these where much larger than Tiangong 1 (77 tonnes and 40 tonnes respectively), both made an uncontrolled re-entry, and in both cases, wreckage did not cause loss of life.

Continue reading “Space Sunday: radiation, rings and pollution”


Space Sunday: Tabby’s Star, NASA’s plans and the Moon’s atmosphere

Is a circumstellar dust ring responsible for the irregular dimming of Tabby’s Star? Credit: NASA/JPL

Yet another study has appeared in an attempt to shed light (pun intended) on the mysterious behaviour of Tabby’s Star.

Regular readers of my Space Sunday columns will recognise this name as belonging to the more formally titled KIC 8462852, an F-type main-sequence star located in the constellation Cygnus approximately 1,480 light years from Earth (and which is also called Boyajian’s Star). This star experiences odd periods of dramatic dimming in its light output every so often (with the Kepler Space Observatory recording a loss of up to 22%), with the fluctuations lasting several solar days before it suddenly resumes its normal luminosity as observed from our solar system.

Many theories have been put forward for what is happening – most of which I’ve covered in these pages. They range from theories about vast alien mega-structures – such as a Dyson sphere, to theories of the star itself suffering what is called “avalanche” activity within itself, to ideas involving huge cometary clouds and giant ringed planets,  or just a single giant ringed planet being responsible.

In the most recent study, Extinction and the Dimming of KIC 8462852, a US / Belgian team of scientists suggest that “none of the above” might actually be the correct answer on why the star goes through its irregular dimming cycle. Instead, they argue tit is the result of a huge but thin and uneven dust ring rotating slowly around the star.  What makes this theory particularly compelling is that it draws on three independently gathered sets of data in order to form the hypothesis.

The first of these data sources is NASA’s Spitzer Space Telescope, used to gather data on Tabby’s Star in the infra-red wave band during December 2016. The second is the Swift Gamma-Ray Burst mission, which gathered data on the star in the ultraviolet band during the same period of observation; also at the same time, the Belgian AstroLAB IRIS Observatory’s 68-cm (27-in) reflecting telescope gathered data in the visible light spectrum.

Artist’s concept of KIC 8462852, which has experienced unusual changes in luminosity over the past few years. Credit: NASA/JPL

What the team found, essentially, was that Tabby’s Star experienced less dimming in the infra-red band than in the ultraviolet – a strong indication that there was a mass of materials, each particle just a few micrometres in diameter, passing between the star and the observatories. While it had been previously suggested the dimming could be the result of an interstellar dust cloud lying somewhere in space between Earth and Tabby’s star, the team discounted this as a possible culprit.

Instead the team took their findings and charted known periods of dimming witnessed with Tabby’s Star and determined a circumstellar dust ring surrounding the star, and rotating around it one every 700 days would actually account for the majority of dimming periods observed from Earth. However, two types of even still do now fit the model.

The first of these is some very short-term “spurts” of dimming which have been noted during 2017. The second is the really large dips in luminosity seen by the Kepler Space Observatory. One potential explanation for the “spurts” of dimming, confirmed through multiple independent observations, is that they might be the result of a cometary cloud orbiting the star and coming between it and Earth. This was actually one of the earliest theories put forward to account for all of Tabby’s Star’s odd behaviour, but it fits the “spurts” of dimming a lot better.

The really big dimming periods, when the star appeared to lose up to 22% of its brightness pose their own problem. They were only observed by Kepler, and have yet to be seen to the same magnitude during any other period of observation, making quantifying them hard. Kepler itself is now studying stars in another portion of the galaxy, so cannot be used to further observe Tabby’s Star to see if such huge dips can again be seen.

Thus, there may yet be another mystery to Tabby’s Star waiting to be solved – or other theories on the fluctuating brightness which may yet be put forward. But for now, the circumstellar dust ring seems to be the most fitting explanation for much of the star’s odd behaviour.

The Moon’s Ancient Atmosphere

That’s the startling conclusion of a new study, supported by NASA’s Solar System Exploration Research Virtual Institute, and recently published in Earth and Planetary Science Letters.

Map of basaltic lavas that emitted gases on the lunar nearside. Credit: Debra Needham
Map of basaltic lavas that emitted gases on the lunar near side. Credit: Debra Needham

That the Moon was subject to intense volcanic activity in its early history is evidenced by the massive  volcanic basalt maria (“seas”) on its surface. From Earth, these form the dark patches and patterns we can see with the naked eye. They were created three to four billion years ago, when the interior of the Moon was still hot and generating magmatic plumes. In places, these broke through the lunar crust, flowing outwards for hundreds of kilometres. Analysis of rock sample returned to Earth by the Apollo astronauts has long revealed these lava flows carried with them gases like carbon monoxide and the ingredients for water, sulphur, and other volatile elements.

In the study, work, Dr. Debra H. Needham, Research Scientist of NASA Marshall Space Flight Centre, and Dr. David A. Kring, Senior Staff Scientist, at the Lunar and Planetary Institute (LPI), used the amounts of trace gases and volatiles in the Apollo samples as a baseline for calculating the probable amount of gases released during those ancient lunar eruptions. Their findings suggest that the gases were released is sufficient quantities over a long enough period of time, reaching its peak around 3.5 billion years ago, to form a transient  lunar atmosphere. It then persisted for about 70 million years after the volcanic activity ended, before the bulk of the gases were lost to space.

Distribution of the volcanic “seas” of the Moon (in blue) – sites of ancient eruptions. Credit: Nasa

The two largest pulses of gases were produced when lava seas filled the Serenitatis and Imbrium basins about 3.8 and 3.5 billion years ago, respectively. The margins of those lava seas were explored by astronauts of the Apollo 15 and 17 missions, who collected the samples that provided the ages of the eruptions.

This new picture of the Moon has important implications for future exploration. The analysis of Needham and Kring quantifies a source of volatiles that may have been trapped from the atmosphere in the cold, permanently shadowed regions near the lunar poles and may well provide a source of ice suitable for a sustained lunar exploration programme. Volatiles trapped in these icy deposits might be used  provide air and fuel for astronauts conducting lunar surface operations.

“We Chose To Go to the Moon, Because That’s What We Were Doing Anyway”

The re-invoked US National Space Council (NSC) held its inaugural meeting n Thursday, October 5th, 2017 at the Smithsonian National Air and Space Museum’s (NASM) Steven F. Udvar-Hazy Centre.

Chaired by the Vice President, the Council was originally  established in 1989 by then-President George H.W. Bush to serve the same purpose as the National Aeronautics and Space Council, which oversaw US space policy between 1958 and 1973. That NSC was disbanded in 1993 by the Clinton administration.

In this first meeting, the NSC sought to overturn NASA’s “Journey to Mars” endeavour in favour of a more focused plan to return to the Moon – or did they?

The inaugural meeting of the re-formed NSC, October 5th, 2017. Credit:  NASA / Joel Kowsky

But how new and bold is this directive?

The reality is, what Pence announced on behalf of the NSC on October 5th and despite all the hurrahs, is pretty much what NASA was already doing anyway, and had been doing since President Obama signed the NASA Authorisation Act of 2010. That is: build the Orion Multi-Purpose Crew Vehicle and the Space Launch System, establish the Deep Space Gateway in cis-lunar space as an “enabler” for lunar missions and missions to Mars, and develop a presence on the Moon while deferring Mars to some nebulous 2030s time frame. The only significant difference is the instruction for NASA to actually flesh-out the lunar outpost element.

On the one hand, this is good, as it means no mass overturning of the apple cart (a favourite past time of incoming administrations)  and a scramble to sort the apples out again. On the other, it still leaves NASA pursuing goals of questionable need – such as the Deep Space Gateway itself. Which, despite all the hype surrounding it, isn’t actually required for either for getting to the Moon or Mars. Rather, it is an objective that’s become fixed in the NASA mindset, and is now being rationalised on the basis that it is part of the mindset, rather than it offering a means to achieve things that cannot be better (and more cost-effectively) achieved through other methods.

What’s in a Name?

Making it safe to reference the “BFR” – the Big “Falcon” Rocket! Credit: SpaceX

At the 68th International Astronautical Congress (IAC) at the end of September, Elon Musk unveiled more of his thinking around sending humans to Mars.

The linchpin of his aspirations is the massive Interstellar Transport System (ITS) rocket SpaceX is developing. This has caused not a few parents some headaches when explaining things to their children, or created a dilemma when explaining the concept in polite company.

It’s not that explaining the ITS concept in complicated. Far from it. Rather, it’s the fact that Musk has chosen to present the ITS launch system using the acronym he originally defined for it: BFR. This, as just about everyone interested in space exploration knows, stands for “big f***ing rocket”. Descriptive yes, given the size of the beast (see right). But suitable for sensitive or young ears? Er, no, possibly not.

So, how does one deal with explaining what “BFR” means to said sensitive / young ears? SpaceX President Gwynne Shotwell recently offered a solution.

While addressing the National Space Council on October 5th, Shotwell – quite probably with a twinkle of humour in his eye –  played on the company’s use of “Falcon” in naming their rockets (the Falcon 9 and Falcon Heavy) to get around the BFR acronym.

“Last week,” he said. “Elon announced — or, basically, gave an update on,” he then paused a bit, before continuing, “the Big Falcon Rocket programme. The Big Falcon Rocket and Big Falcon Spaceship.”

So there you have it, a non-offensive and semi-accurate way to explain “BFR” to the kids!


Space Sunday: Mars visions, gateways and James Webb

Elon Musk has bold plans for building a permanent human presence on Mars. Credit: SpaceX

The 68th International Astronautical Congress (IAC) ran from September 25th to September 29th, 2017 in Adelaide, Australia, and brought forth a plethora of announcements, presentations and updates from all those involved in space exploration.

one of the more attention-grabbing announcements came – unsurprisingly – from Elon Musk and SpaceX. Already leading the way in private sector launches and launch vehicle reusability,  SpaceX has in many respects set the bar for the launch industry as a whole. Musk, meanwhile has raised eyebrows with his longer-term goals, which focus on human missions to Mars and – eventually – the colonisation of the Red Planet. At the September 2016 IAC, he laid the outlines for achieving these goals, and in 2017 he returned to the IAC to offer further updates and insights to the SpaceX approach.

Most surprisingly, given the company’s reliance on it for revenue generation, Musk indicated that he is prepared to phase out all Falcon 9 launch operations, including the yet-to-fly Falcon Heavy, at some point in the near future in order to focus the company on the development and operation of its Interplanetary Transport System (ITS), which Musk still likes to refer to as the BFR (for “Big F***ing Rocket” on account of its overwhelming size).

The updates ITS launcher, seen here in comparison to the Falcon 9 and Falcon Heavy, will be 106 metres tall, powered by 31 first stage engines (down from the original 42), and capable of lifting 150 tonnes to low Earth orbit. Credit: SpaceX

Fabrication of parts of the first ITS launcher – which is the linchpin for Musk’s Mars ambitions – has been in progress for some time, and SpaceX hope to start on the assembly of the first vehicle in the series in mid-to-late 2018. Musk is now so confident in the vehicle’s development status, he is hoping to have two of the launch vehicles ready to fly cargo missions to Mars during the 2022 launch opportunity – although he emphasised this time frame is “aspirational” rather than a fixed deadline.

This version of the ITS will be slightly scaled-down from the version announced last year, reducing the overall launch height and mass of the vehicle, and the number of main engines it will require – 31 instead of 42. The 2022 mission will have a two-fold purpose: deliver core components required for human operations on Mars to the surface of the planet; located subsurface water / water ice which could be extracted and used to generate oxygen which could be used within the atmosphere of a future base, and as an oxidizer in fuel used by vehicles making the return flight to Earth.

The upper stage of the ITS is an interplanetary craft powered by a mix of methane (CH4) and oxygen (both of which can be manufactured on Mars, allowing the craft to be re-fuelled there for return flights to Earth) and carrying either cargo in its upper section, or up to 100 passengers in 40 cabins and common crew spaces which offer living space in excess of the space found in an Airbus A380 airliner. Credit: SpaceX

According to Musk, should this mission proceed to plan, it will be followed in 2024 by four craft carrying a mix of equipment, supplies and crews to Mars to commence human exploration of the planet.

All of this is highly ambitious, technically and financially. On the technical front, there are significant issues to be addressed, most notably – but not limited to – that of the radiation threat posed by Galactic Cosmic Rays (GCRs). As I’ve pointed out in past Space Sunday articles on this subject, solar radiation – often seen as “the” radiation threat – can be managed relatively well, simply because it is generally low-energy radiation.

The ITS upper stage on the pad at Musk’s future Mars colony and awaiting refuelling / a return to Earth. Credit: SpaceX

GCRs, however, are high-energy particles which are much harder to deal with: and there is a lot of them in interplanetary space to deal with. Data from the Mars Science Laboratory’s flight to Mars in 2012 revealed that an unprotected astronaut on a similar flight would face the equivalent radiation dose as having a full-body CAT scan every 5-6 days for six months – definitely not a healthy proposition. There are technologies  being developed which can mitigate GCRs, such as such as hydrogenated boron nitride nanotubes (BNNTs), but these are still some way from being available for general use in spacecraft and spacesuit designs. Musk didn’t expand on how SpaceX plan to handle things like GCRs.

He was, however, more forthcoming on how SpaceX would finance the construction and operation of the ITS system. firstly, SpaceX will build up a “stock” of Falcon 9 units which could be used (and re-used) as launchers and components for Falcon Heavy launchers. Secondly, and once available, the revised ITS will be offered as a commercial launch vehicle capable of placing 100 tonnes into low Earth orbit and delivering objects to geostationary orbit or the moon; payloads could be single large items or multiple items. The plan is to use the stock of Falcon boosters through until customers have confidence in the ITS launcher (which will also be reusable) in order to switch over to using it, after which, all Falcon operations will be phased out.

Musk plans to offer the ITS for launches to LEO, the space station, geostationary orbit and even to the Moon for cargo flights, etc. Shown here, an ITS upper stage with solar panels deployed, releases a large single payload into LEO. Credit: SpaceX

In addition, and with usual Musk showmanship, the entrepreneur indicated further revenue could be obtained by offering sub-orbital aerospace flights between major cities in record time. According to his calculations, he claimed that such flights could ferry customers between Bangkok and Dubai in just 27 minutes, or between Tokyo and Delhi in 30 minutes, using a smaller variant of the ITS.

Quite how these system would work or how the necessary support infrastructure needed to support launch / recovery / refurbishment operations around the globe would be financed was not made clear – nor was the potential cost of tickets.

Continue reading “Space Sunday: Mars visions, gateways and James Webb”

Space Sunday: rovers, robots, rockets and space stations

NASA’s Mars Science Laboratory rover Curiosity has begun the steep ascent of an iron-oxide-bearing ridge that’s grabbed scientists’ attention since before the mission arrived on Mars in 2012.

“Vera Rubin Ridge”, previously referred to as “Hematite Ridge”, stands prominently on the north-western flank of Mount Sharp, resisting erosion better than the less-steep portions of the mountain below and above it.

“We’re on the climb now, driving up a route where we can access the layers we’ve studied from below,” said Abigail Fraeman, a Curiosity science-team member. As we skirted around the base of the ridge this summer, we had the opportunity to observe the large vertical exposure of rock layers that make up the bottom part of the ridge. But even though steep cliffs are great for exposing the stratifications, they’re not so good for driving up.”

The ascent to the top of the ridge will take the rover through a 65 metre (213 ft) change in elevation, which is being achieved through a series of drives which started in early September 2017, and which will cover a distance of around 470 metres (1542 ft).

Vera Rubin Ridge mosaic of 70 images captured by Curiosity’s Mastcam telephoto lens on August 13th, 2017. The layering of the ridge can clearly be seen. Credit: NASA/JPL / MSSS

The ridge is of particular interest to scientists not only for its erosion resistant composition, but also because the rock of the ridge exhibits fine layering, with extensive bright veins of varying widths cutting through the layers. Orbital spectrometer observations have revealed the iron-oxide mineral hematite shows up more strongly at the ridge top than elsewhere on lower “Mount Sharp”, including locations where Curiosity has already found the mineral. It is hoped that a detailed study of the ridge will reveal why it has been so resistant to erosion and whether this is related to the high concentrations of hematite in the rock. Answering these questions could further reveal information on past environmental conditions within Gale Crater.

“The team is excited to be exploring Vera Rubin Ridge, as this hematite ridge has been a go-to target for Curiosity ever since Gale Crater was selected as the landing site,” said Michael Meyer, lead scientist of NASA’s Mars Exploration Programme at the agency’s Washington headquarters.

A monochrome image of “Vera Rubin Ridge” captured using the imager on Curiosity’s ChemCam instrument shows sedimentary layers and fracture-filling mineral deposits. ChemCam’s telescopic Remote Micro-Imager took the 10 component images of this scene on July 3rd, 2017, from a distance of about 377 feet. Credit: NASA/JPL / CNES / CNRS / LANL / IRAP / IAS / LPGN

Curiosity Project Scientist Ashwin Vasavada of JPL added, “Using data from orbiters and our own approach imaging, the team has chosen places to pause for more extensive studies on the way up, such as where the rock layers show changes in appearance or composition. But the campaign plan will evolve as we examine the rocks in detail. As always, it’s a mix of planning and discovery.”

In the meantime, and in the saw-sawing of evidence concerning the past habitability of Mars, a team from the Los Alamos National Laboratory (LANL) has discovered evidence of boron on Mars, adding weight to the pro-life side of the argument.

A key building block of modern life is ribonucleic acid (RNA), which requires the sugar ribose. Like all sugars, ribose is unstable and quickly dissolves in presence of liquid, particularly water. However, when boron is dissolved in water it becomes borate, which acts as would act as a stabilising agent of ribose, keeping the sugar together long enough so that RNA can form.

“Borates are one possible bridge from simple organic molecules to RNA,” Patrick Gasda, the lead author of the LANL paper outlining the discovery. “Without RNA, you have no life. We detected borates in a crater on Mars that’s 3.8 billion years old, younger than the likely formation of life on Earth.”

An artist’s impression of how the lake in Gale Crater may once have looked. The central “island” is the impact peak and humped formation of “Mount Sharp”. Credit: Kevin M. Gill

The mineral was detected by Curiosity’s ChemCam instrument, a joint development by LANL the French space agency, the National Center of Space Studies (CNES). It was found in veins of calcium sulphate minerals located in the Gale Crater, indicating it was present in Mars’ groundwater and was preserved with other minerals when the water dissolved, leaving behind rich mineral veins.

Curiosity has already confirmed that Gale Crater was home to a series of lakes, and the LANL findings add weight to the potential these lakes could have had life in them at a time when it would have experienced temperatures ranging from 0 to 60 ° C (32 to 140 °F) and had a pH level that would have been neutral-to-alkaline.

OSIRIS-REx Swings by Earth

Just over a year ago, on September 8th, 2016, NASA’s Origins, Spectral Interpretation, Resource Identification, Security – Regolith Explorer (OSIRIS-REx) lifted-off from Space Launch Complex 41 at Cape Canaveral Air Force Station, at the start of a journey which will carry it a total of 7.2 billion kilometres (4.5 billion miles) to gather samples from the surface of an asteroid and return them to Earth for study (see my previous reports here and here).

On September 22nd, 2017, the spacecraft returned to the vicinity of Earth – albeit it briefly –  to gain the gravity assisted speed boost it needs in order to complete its journey to the carbon rich asteroid Bennu, from which it will gather samples.

A graphic issued ahead of the OSIRIS-REx fly-be on Friday, September 22nd. Credit: NASA’s Goddard Space Flight Centre / University of Arizona

In making the flyby, the spacecraft came to within 17,000 km (11,000 mi) of Earth, approaching at a speed of around 30,400 km/h (19,000 mph) and passing over Australia and Antarctica, gaining a velocity boost of around  13,400 km/h (8,400 mph) as it accelerated back out into the solar system. The fly-by also curved the probe’s course onto an intercept trajectory with Bennu, which it will reach in October 2018. During the operation, OSIRIS-REx performed a science campaign, collecting images and data from Earth and the Moon, which also allowed the science team to check and calibrate the probe’s suite of science instruments.

Bennu is roughly 450 metres (1,614-ft) in diameter, and its solar orbit carries it across that of the Earth  every six years. It is carbon rich, which is of significant interest to scientists because carbonaceous material is a key element in organic molecules necessary for life, as well as being representative of matter from before the formation of Earth. Organic molecules, such as amino acids, have previously been found in meteorite and comet samples, indicating that some ingredients necessary for life can be naturally synthesised in outer space.

On reaching Bennu, OSIRIS REx will “fly” alongside the asteroid for some 12 months, surveying and studying it and imaging points of interest as possible candidates for a daring “touch and go” sample gathering mission, when it will collect between 60 and 2000 grams (2–70 ounces) of material. If all goes well, the probe will depart Bennu in March 2021, arriving back at Earth in September 2023, when the sample will be parachuted down for scientists to study.

A secondary reason for visiting Bennu is that, like many Near-Earth Asteroids (NEAs) there is a slim chance it might strike our planet towards the end of the 22nd Century. An analysis of the thermal absorption and emissions of the asteroid will allow scientists to better predict its future orbits and the real potential for such a collision, and could help determine the actual risk of other NEAs striking Earth.

Continue reading “Space Sunday: rovers, robots, rockets and space stations”