Space Sunday: to touch the face of the Sun

Ignition! The three main stages of the Delta 4 Heavy fire, starting the Parker Solar Probe on its mission to examine the Sun up close and personal. Credit: NASA

On the morning of Sunday, August 12th, 2018, NASA launched the Parker Solar mission, which it describes as being “to touch the face of the Sun”. It will be the first mission to fly through the Sun’s corona – the hazardous region of intense heat and solar radiation in the Sun’s atmosphere that is visible during an eclipse, and it will gather data that could help answer questions about solar physics that have puzzled scientists for decades. Over the course of its initial 7-years the Parker Solar Probe mission will allow us to better understand the fundamental processes going on in, on, and around the Sun, improving our understanding how our solar system’s star influences, affects and changes the space environment, through which we travel as the Earth orbits the Sun.

The probe and mission are named for Dr Eugene Parker, an American solar astrophysicist, who in 1958 first posited  the theory of the supersonic solar wind, and who also predicted the Parker spiral shape of the solar magnetic field in the outer solar system. Now 91, he was present at NASA’s Kennedy Space Centre as a distinguished guest of the agency, to witness the probe’s launch, the mission (and vehicle) being the first in NASA’s history to be named after a still-living person.

The Delta 4 Heavy carrying the Parker Solar Probe sits on the pad of Space Launch Complex (SLC) 37 at Canaveral Air Force Station, Florida, following the aborted launch attempt of Saturday, August 11th, 2018. Credit: Vikash Mahadeo / SpaceFlight Insider

Lift-off came at 03:31 EDT (6:31 GMT / 7:31 BST) on Sunday, August 12th, after the initial launch attempt was scrubbed on Saturday, August 11th, when a troubled countdown was halted just one-minute, 55 seconds before the engines on the United Launch Alliance (ULA) Delta 4 Heavy rocket were to ignite. The halt was called following a gaseous helium red pressure alarm, and investigations into its cause extended beyond the 65-minute launch window, resulting in the launch scrub.

The Sunday morning launch countdown proceeded without any significant hitches, and the Delta 4 Heavy – the most powerful rocket in ULA’s fleet of launch vehicles, comprising 3 Delta 4 first stages strapped side-by-side, the outer two functioning as “strap-on boosters” – lit up the Florida coastline as it took to the early morning skies.

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Although a flight to the Sun might sound an easier proposition than reaching the outer solar system, it actually isn’t; it actually requires 55 times more launch energy than a launch to Mars. Hence why the relative small and light Parker Solar Probe, weighing just 685 kg (1,510 lb) at launch, required the massive Delta 4 and a rarely-used Star 48BV variant of the Payload Assist Module (PAM).

Originally developed as the upper stage for Delta 2 launch vehicles in the 1965, the Star family of solid-fuel PAM units were commonly used with the space shuttle for satellite launches from orbit: the shuttle would carry them aloft, release the PAM / Satellite combination, then move to a safe distance before the PAM motor was ignited to push the satellite on to its require Earth orbit. For the Parker Solar Probe, the Star 48BV was used to impart as much velocity as possible into the vehicle at is starts on it journey.

Dr. Eugene Parker, now 91, watches the launch of the probe named in his honour as it lifts-off from SLC-37, Sunday, August 12th, 2018. Credit: NASA / Glenn Benson

What makes a flight to the Sun so hard is that the Earth is moving “sideways” relative to the Sun at about 107,000 km/h (67,000 mph), and the probe has to cancel out a whopping 84,800 km/h (53,000 mph) of that “sideways” motion as it makes its way to the Sun in order to achieve orbit. At the same time, the probe needs to gain velocity as it moves in towards the centre of the solar system in order for it to balance the Sun’s enormous gravitational influence and achieve the required elliptical orbit.

The use of the Delta 4 / Star 48BV combination got both of these requirements started, by pushing the probe towards Venus in an arc that will both start to shed the “sideways” velocity, whilst also accelerating the craft in towards the Sun. But it will be Venus that does the real grunt work for the mission.

On October 1st, 2018, the probe will make the first of a series of flybys of Venus, where it will use the Venusian gravity to shed still more of the angular velocity imparted by Earth’s orbit and increase its velocity towards the Sun.

In all, seven such fly-bys of Venus will occur  over the 7 year primary mission for the probe, and while only the first is required to shunt the vehicle into its core heliocentric orbit, the remaining six play an important role in both maintaining the vehicle’s average velocity across the span of the mission and in gradually shrinking its elliptical orbit around the Sun as the mission progresses.

The first pass around the Sun  – and the start of the science mission – will occur in November / December 2018. At perihelion, the vehicle will be just 6.2 million km (3.85 million mi) from the Sun’s photosphere (what we might call its “surface”). During this time, the vehicle will be well within the corona, and will also temporarily become the fastest human-made vehicle ever made, achieving a velocity of around 700,000 km/h (430,000 mph) – that’s 200 km per second (120 mi/s), or the equivalent of travelling between London and Tokyo in around 50 seconds! At aphelion – the point furthest from the Sun, and brushing Earth’s orbit, the craft will be travelling a lot slower.

The corona is a very hot place – hotter than the “surface” of the Sun, however, it is also comparatively thin as far as an “atmosphere” goes. The distance at which Parker Solar Probe will be travelling from the Sun at perihelion, combined with its speed, mean that the ambient heat of the corona isn’t a significant issue. Direct sunlight radiating out from the Sun, however, is a significant problem.

Continue reading “Space Sunday: to touch the face of the Sun”

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Space Sunday: questions of life, and the “Commercial Nine”

A computer generated terraformed Moon. While it may not have looked like this in its past, the Moon may once not only have had an atmosphere and liquid water on its surface, it may have had conditions suitable for life. Credit: unknown, via Lunar wikia

Throughout human history – and outside of flights of fancy – the Moon has always been thought of as an airless ball of rock, tidally locked to Earth so that it shows the same, almost never-changing face to us in the night sky. But it may not always have been so.

In recent years, our perceptions of the Moon have been changing as a result of a number of studies and missions. In 2009, for example, India’s first lunar mission, Chandrayaan I, produced a detailed chemical and mineralogical map of the lunar surface, revealing the presence of water molecules in the lunar “soil”. In that same year, NASA launched a pair of missions to the Moon, the Lunar Reconnaissance Orbiter (LRO) mission and the Lunar Crater Observation and Sensing Satellite (LCROSS).

LCROSS was a small satellite designed to follow the upper stage of the rocket used to launch it and LRO to the Moon and analyse the plume of debris created by the impact of the upper stage with Cabeus crater in the Moon’s south polar region. The impact came with a kinetic energy equivalent of an explosion created using 2 tons of TNT, and LCROSS recorded strong evidence of water within the resultant impact plume.

For its part, LRO entered lunar orbit to commence a comprehensive campaign of mapping, imaging and probing the Moon’s surface and environment. In doing so, it further confirmed the presence of abundant concentrations of water in the lunar south polar regions. At the same time and LRO has been studying the Moon, an ongoing analysis of the rock samples brought back by the Apollo astronauts has revealed strong evidence for a large amount of water being present in the lunar mantle – possibly as much as is present in Earth’s upper mantle.

An artist’s impression of the 2009 LCROSS satellite “shadowing” the Centaur upper stage used to launch both it and the Lunar Reconnaissance Orbiter (LRO), as the upper stage heads towards its lunar impact. Credit: NASA

These results and findings have given rise to the idea that very early on in the Moon’s history conditions could have been very different to how it is now. In the immediate period following the Moon’s creation (roughly four billion years ago), there are a period when it was very volcanically active (about 3.8-3.5 billion years ago), releasing considerable amounts of superheated volatile gasses, including water vapour, from its interior. This outgassing could have given rise to an atmosphere around the Moon dense enough to support that water vapour condensing out into liquid on the surface which could have conceivably lasted for several million years whilst the atmosphere remained dense enough to support it, before it either (largely) evaporated or retreated underground to eventually freeze.

In their new study, published in July 2018, Dirk Schulze-Makuch, a professor of astrophysics at Washington State University, USA, and Ian A. Crawford, a professor of planetary science and astrobiology at Birkbeck College, University of London, UK, review the evidence for liquid water to have been present on the Moon and examine the potential for it to have been life-bearing. In particular, they note that when all is said and done, if the early conditions on the Moon did give rise to a dense atmosphere and a water-bearing surface, then the conditions there wouldn’t have been that different to those being experienced on Earth when life here was starting up, and would have occurred in the same time frame.

A false-colour image of the Moon’s south pole highlights areas that are in permanent shadow. These account for around 3% of the south polar region, and could be places where frozen water exists beneath the surface (note the blue colour is not indicative of water, but simply a means of highlighting the shadow spots). Credit: NASA Goodard Space Centre

It looks very much like the Moon was habitable at this time. There could have actually been microbes thriving in water pools on the Moon until the surface became dry and dead.

Dirk Schulze-Makuch, co-author of Was There an Early Habitability Window for Earth’s Moon?,
quoted in Astrobiology Magazine

So does that mean life, however transient, got a start on the Moon? Possibly; however, some have suggested rather than giving rise to life directly, the conditions on that early Moon might have been ideal for life from Earth to gain a toe-hold.

As noted, the period when the Moon may have had its dense atmosphere coincided with life starting on Earth in a period referred to as the Late Heavy Bombardment, (4.1 and 3.8 to 3.5 billion years ago). During that time, bacteria such as cyanobacteria were believed to be already present on Earth, even as it was being bombarded by frequent giant meteorite impacts (hence the period’s name). So the suggestion is that this bombardment could have thrown chunks of bacteria-laden rock into space, where they were “swept up” by the Moon, transferring the bacteria to its surface, where it might have taken hold.

It’s unlikely that if it go started, life on the Moon got very far; within a few million years after the end of the Moon’s volcanic period the atmosphere would have been lost, and conditions would have become far too harsh for life to endure. However, in noting this, Crawford and Schulze-Makuch use their study as a call for a more robust study on the potential ancient habitability of the Moon, including a hunt for possible biomarkers.

Not related to the article: this image taken by LRO in 2011 highlights the Apollo 17 landing site and areas explored by Gene Cernan and Harrison Schmitt in 1972. Credit: NASA / NASA Goddard Space Centre.

Such an endeavour would likely be focused on the lunar south polar regions, simply because of the potential abundance of subsurface frozen water there. And as it is, NASA, India and China are already committed to studying the region in great detail. NASA will initially do so from orbit, while the Indian Chandrayaan-2 mission will attempt to place a lander and rover close to the Moon’s south pole in 2019. Also in 2019, China will send its  Chang’e 5 mission to the Moon’s north polar regions to gather and return around 2 kg of rock samples for detailed analysis on Earth.

Continue reading “Space Sunday: questions of life, and the “Commercial Nine””

Space Sunday: an eclipse, a space ship, lasers and a birthday

The total lunar eclipse as seen over the columns of the acropolis. Greece, on July 27th, 2018. Credit: Valerie Gache / AFP Getty Images

Friday, July 27th marked the longest lunar eclipse of the 21st century, which was visible from southern Africa, Australia, and Madagascar, Europe, South Asia and South America. Although many of us in the UK largely (and typically!) missed out, as the summer heat wave gave way to rain and clouds, a bit of a double blow, given we were just outside the reach of totality.

For about half the world, the Moon was partly or fully in Earth’s shadow from 17:14 to 23:28 GMT; six hours and 14 minutes in all, with the period of totality – when the Moon lies entirely within the Earth’s shadow, and so is at its darkest – lasting from 19:30 to 21:13 GMT.

Another view of the eclipse from Greece: the Moon appears between the ancient gods Apollo and Hera in Athens. Credit: Aris Messinisaris / AFP / Getty Images

In a special treat, Mars, which is currently at opposition, sitting on the same side of the Sun as Earth, and thus at its closest to Earth (roughly 92 million km /  57 million mi), was visible just below the eclipsed Moon, appearing as a bright “star”. Those blessed with clear skies also had the treat of Saturn, Jupiter and Venus being visible in the sky as well.

The reason the eclipse lasted so long was that the alignment between Sun, Earth and Moon meant that the Moon was passing right across the middle of the disc of shadow cast by the the Earth. This also meant this eclipse created a particularly strong blood Moon. This is a phenomena caused by the lensing effect of the Earth’s atmosphere scatters blue light from the Sun outwards, whilst refracting red light inwards, so the Moon appears rusted as  seen from Earth.

The July 2018 blood moon, seen from Siliguri, India, on July 28th, 2018 (local time). Credit: Diptendu Duttadiptendu Dutta / AFP /Getty Images

Virgin Galactic Reach Mesosphere for the 1st Time

VSS Unity took to the skies on July 26th, 2018, and reached its highest altitude yet: 52,000 metres (170,800 ft), the highest any Virgin Galactic vehicle has thus far reached.

VMS (Virgin Mother Ship) Eve, the WhiteKnightTwo carrier aircraft, took off from the Mojave Spaceport at 15:45 GMT and climbed to an altitude of 14,000 metres (46,500 ft), prior to releasing Unity, which dropped clear prior to its single rocket motor being ignited. The engine burned for some 42 seconds, powering the vehicle into a near vertical ascent and a speed that reached Mach 2.47.

This was enough to propel Unity on a parabolic flight that topped-out at 52,000 m, inside the mesosphere, which spans heights from approximately 10 km (33,000 ft; 6.2 mi) to 100 km (62 mi; 330,000 ft), representing the heights to which Virgin Galactic flights will typically carry fare-paying passengers so they can enjoy around 5 minutes of weightlessness.

VSS Unity mid-flight on July 26th, 2018, as seen from a chase plane. Credit: Virgin Galactic / MarsScientific.com / Trumbull Studios

It was a thrill from start to finish. Unity’s rocket motor performed magnificently again, and Sooch [co-pilot Mike Masucci] pulled off a smooth landing. This was a new altitude record for both of us in the cockpit, not to mention our mannequin in the back, and the views of Earth from the black sky were magnificent.

– Virgin Galactic’s chief pilot, Dave Mackay

The mesosphere is sometimes referred to the “ignorosphere”, as it sits above the range of instrument carrying balloons, but well below the height from which it can be studied from space, and so remains one of the least-studied parts of the atmosphere. As well as carrying passengers aboard their vehicles, Virgin Galactic plan to change this by also flying experiments up to the mesosphere that might be used to probe it.

VSS Unity about to touch down, July 26th, 2018. Credit: Virgin Galactic

As with previous flights, today’s test flight was designed in part to gather additional data about conditions in the cabin during flight, but it also marks a significant step closer to the company starting commercial tourist flights, which are currently earmarked to commence in 2019, or possibly the end of 2018. Before that, however, the company will make at least one flight  with Unity’s motor fuelled for a full duration burn of 60 seconds. When that might be, and whether it might follow  directly on from this flight (which represented an 11 second longer engine burn than previous flights) or be worked up to, has yet to be stated.

When operational, VSS Unity will be joined by at least two more SpaceShipTwo vehicles, and – at some point in the next couple of years – an additional WhiteKnightTwo carrier vehicle, given the company are looking to operate flights out of Italy as well.

Continue reading “Space Sunday: an eclipse, a space ship, lasers and a birthday”

Space Sunday: of rockets and planets

SpaceX Crew Dragon (l) and the Boeing CST-100 Starliner: Further delays could threaten US access to the ISS. Credit: SpaceX / Boeing

The first SpaceX Crew Dragon (aka Dragon 2) vehicle destined to fly in space has arrived in Florida ahead of its launch, due in August 2018. The capsule is intended to be part of an uncrewed first flight to test the vehicle’s flight test systems.

Prior its transfer to Kennedy Space Centre (KSC), the capsule and service module were the subject of extensive thermal vacuum chamber tests at NASA’s Plum Brook Station in Ohio. The world’s only facility capable of testing full-scale upper-stage launch vehicles and rocket engines under simulated high-altitude conditions, the chamber is a vital part of pre-launch testing – although by the date of the capsule’s arrival at KSC, the results of the Ohio testing had not been made public.

SpaceX’s first Crew Dragon spacecraft is prepared to undergo testing at the In-Space Propulsion Facility of NASA’s Plum Brook Station in Sandusky, Ohio on June 13th, 2018. Credit: SpaceX

No official date for the first Crew Dragon flight has been released, but SpaceX are pushing ahead with work to prepare the vehicle for launch, in anticipation of the flight being given the green light for August. The test flight should see the uncrewed test vehicle fly to the International Space Station (ISS), with a follow-up 14-day crewed test flight due to take place in late 2018 / early 2019.

The arrival of the Crew Dragon test article at KSC came at the same time as a further US government report raised concerns about both SpaceX and Boeing – the other company contracted to make crewed flights to / from the ISS using their CST-100 Starliner capsule – being able to meet the current schedule for commencing formal operations.

A July 11th, 2018, report from the independent Government Accountability Office (GAO) points out that if any significant issues arise with either / both vehicles prior to their formal certification, it could see one or other or both companies being unable to commence active crew launches within the anticipated time frames specified by NASA. Were this to be the case, America would effectively be without the means to send astronauts to the Space Station, as the current contract to fly US crew aboard Russian Soyuz vehicles expires in November 2019.

Under the original schedule, the Boeing CST-100 was to have been certified for crew operations in January 2019, and the Crew Dragon in February 2019. However, both these dates were recently revised: the CST-100 certification slipping to December 2019 and Crew Dragon’s to February 2020.

With crew rotations to the ISS lasting 6 months, this slippage – which moved the first official crewed flights of both CST-100 and Crew Dragon to several months after the Soyuz contract ends – were not seen as a significant issue. However, the GAO report warns that certification of both vehicles could slip to around August 2020 should difficulties with either / both vehicles be encountered as a result of the test flights (or other reasons). This would potentially see a nine-month gap open between the last of the planned US Soyuz flights and a commencement of CST-100 / Crew Dragon flights, more than the span of a crew rotation, with no contingency currently in place to allow continued US access to the ISS until either of the new vehicles is ready to fly.

A “Temperate” Exoplanet?

Ross 128 is a red dwarf star just 11 light-years away from our Sun that over the years has been a source of interest for astronomers. First catalogued in 1926, the star is too faint to be seen with the naked eye, but is classified an old disk star with a low abundance of elements other than hydrogen and helium. Like most red dwarf stars, Ross 128 is given to violent flare activity, although its extreme age makes such events a lot less frequent than “younger” red dwarfs.

In mid-2017, Ross 128 caused something of a stir when a mysterious burst of signals was recorded apparently coming from its general vicinity. Dubbed the “Weird!” signals, the series of unusual “transmissions” were received by the  Arecibo radio telescope, Puerto Rico on May 12th/13th, 2017.

The 2017 Weird! signal that seemed to come from Ross 128 (but has never been re-acquired). Credit: UPR Aricebo

At the time, the signals caused a lot of excitement and talk of “aliens” being involved – although no planets had actually been detected around Ross 128. As I reported in July 2017, after further study, it was determined that the most likely explanation for the signals was that they’d been accidentally picked up from satellites occupying the same part of the sky as Ross 128 at the time Aricebo happened to be listening; all attempts to re-acquire them by numerous radio telescoped failed to do so.

While there is no reason to change the view that the odd signals of May 2017 were from local satellites rather than originating with Ross 128, in November 2017 it was confirmed the star does in fact have a planet orbiting it.

Referred to as Ross 128 b, the planet was first detected in July 2017 by a team operating the High Accuracy Radial velocity Planet Searcher (HARPS) instrument at the La Silla Observatory in Chile. However, it was not until November of 2017 that the astronomers were able to confirm that had located the planet.  Since then, the planet has been the subject of indirect scrutiny to try to better determine its characteristics, and the results are interesting.

The HARPS data initially suggested the planet to be roughly around the size of Earth and orbiting in the star’s habitable zone. However, further characterisation of the planet – including whether or not it has an atmosphere – has been hampered by the fact that its orbit around its parent star means it doesn’t actually transit between Ross 128 and Earth.

An artist’s impression of Ross 128 b orbiting its parent star. Credit: ESO/M. Kornmesser

As this presents a barrier to analysing the planet directly by the effect it and its atmosphere (if it has one) has on light coming from its parent star, astronomers instead turned to studying Ross 128 itself in their attempts to better understand the potential nature of Ross 128 b.  In particular, a team led by Diogo Souto of Brazil’s Observatório Nacional used Sloan Digital Sky Survey‘s APOGEE spectroscopic instrument to measure the star’s near-infrared light to derive abundances of carbon, oxygen, magnesium, aluminium, potassium, calcium, titanium, and iron.

Continue reading “Space Sunday: of rockets and planets”

Space Sunday: asteroids, telescopes and dust

Credit: Mopic/Shutterstock

Saturday, June 30th marked International Asteroid Day, a global event involving researchers, astronomy groups, space agencies and more talking about asteroids  – and the risk some of them present to Earth.

Since 2013, and the Chelyabinsk event which saw a meteor  roughly 20 metres across, caught on film as it broke up high over the Russian town, the tabloid media has seemingly been obsessed with reporting meteors about to collide Earth and wreak havoc.

Fortunately, the vast majority of the estimated 10 million objects which have orbits passing close to Earth – referred to as NEOs, for Near Earth Objects, are unlikely to actually strike our atmosphere or are of a small enough size not to pose a significant threat if they did, despite all the screaming of the tabloids.

A map showing the frequency of small asteroids entering Earth’s atmosphere between 1994 and 2013. The dot sizes are proportional to the optical radiated energy of impacts measured in billions of Joules (GJ) of energy. A total of 556 events are recorded on the map, representing objects ranging in size from 1m to 20m. Credit: NASA’s Near Earth Object (NEO) programme

Which is not to say NEOs don’t pose a potential threat. Not all of the 10 million objects with orbits passing close to, or intersecting, the orbit of Earth have been properly mapped. Take 2018 LA (ZLAF9B2), for example. As I reported at the start of June, this asteroid, some 2 metres across, was only identified a handful of hours before it slammed into Earth’s upper atmosphere over Botswana at approximately 17,000 kilometres per second, to be caught on film as it burnt up. The energetic force of the accompanying explosion has been estimated to have been in the region of 0.3 to 0.5 kilotons (300 to 500 tonnes of TNT).

To offer a couple of quick comparisons with this event:

  • The 2013 Chelyabinsk superbolide (roughly 10 times the size of 2018 LA (ZLAF9B2) disintegrated at an altitude of around at 29.7 km at a velocity between 60,000-69,000 km/h, producing an energy release equivalent to 400-500 kilotons (400,000-500,000 tonnes of TNT). This was enough to blow out windows and send 1,491 people to hospital with injuries, including several dozen temporarily blinded by the flash of the explosion. The first 32 seconds of the video below convey something of the force of that event.

  • In June 1908 a cometary fragment estimated between 60 and 190 metres cross disintegrated some 5 to 10 km above Tunguska, Siberia. This generated an estimated downward explosive force of between 3 to 5 megatons and an overall force of somewhere between 10 to 15 megatons (again for comparison, all the bombs dropped by allied forces in World War 2 amounted to around 3.4 megatons of combined explosive force). This is believed to have generated a shock wave measuring 5.0 on the Richter scale, flattening an estimated 80 million trees covering an area of 2,150 square kilometres. Were it to occur today, such an event would devastate a large city.

There are two sobering points with these two events. The first is that astronomers estimate only about one-third (1600) of objects the size of the Tunguska event meteoroid which might be among that 10 million NEOs have so far been mapped. The second is that many NEOs can remain “hidden” from our view. the Chelyabinsk superbolide, for example passed unseen as the Sun completely obscured its approach to Earth.

There have been several proposals for trying to deal with the potential risk of a PHA – Potentially Hazardous Asteroid – impact over the years. One currently in development is the NASA / Applied Physics Laboratory (APL) Double Asteroid Redirection Test (DART) mission intended to demonstrate the kinetic effects of crashing an impactor spacecraft into an asteroid for planetary defence purposes.

The target for this mission is rather interesting. DART will be launched on an intercept with 65803 Didymos, an asteroid around 750 metres across – but this will not be the vehicle’s target. That honour goes to a much smaller asteroid – around 170 metres across (so in the size range of the Tunguska object) – orbiting 65803 Didymos and informally referred to as “Didymoon”.

Originally, DART was to be a part of a joint NASA/APL and European Space Agency effort, with ESA supplying a vehicle called the Asteroid Intercept Mission (AIM). This would have been launched ahead of DART on a trajectory that would place it in orbit around the 65803 Didymos / “Didymoon” pairing, allowing it to track / guide DART to its target and record the entire impact and its aftermath.

AIM never received funding, leaving the NASA/APL mission, which is currently scheduled for launch in 2021 and will intercept “Didymoon” in 2022. However, in the last few weeks, ESA has announced a revised mission to 65803 Didymos called Hera. Like AIM, it is designed to orbit the asteroid and is moon, and a call has been made to combine it with DART under a new joint mission called Asteroid Impact and Deflection Assessment (AIDA).

This would require DART to be delayed for a number of years to give ESA time to obtain approval for Hera and design, build and launch the craft – so the intercept would not take place until 2026. While this is a delay, it would mean that scientists would be able to better characterise “Didymoon” ahead of DART’s arrival, and witness the impact and its aftermath in real-time.

The original DART / AIM mission – to study the use of kinetic vehicles to divert an asteroid – now potentially superseded by the DART / Hera mission. Credit: NASA / APL / ESA

It’s not clear whether or not DART will be delayed. If it isn’t, then it has been proposed DART carries a camera equipped cubesat similar to those AIM would have used in support of its mission. This could then be separated from DART ahead of the impact so it could image the event as it flies by “Didymoon”. The Hera mission would then arrive a few years after the impact and assess the outcome, including imaging the impact crater on the asteroid and changes to its orbit and its rotation, which can help scientists determine how efficient the impact was in transferring its energy into “Didymoon”.

Continue reading “Space Sunday: asteroids, telescopes and dust”

Space Sunday: stations, Ceres, doubts and rockets

Tiangong-2, with one of the two docking ports visible. Credit: China News

China may be preparing to de-orbit its Tiangong-2 orbital laboratory, possibly to avoid a situation similar to that relating to the so-called “uncontrolled” re-entry of their Tiangong-1 facility, which re-entered the Earth’s atmosphere and broke-up / burnt-up in April 2018.

Orbital information published by the U.S. Strategic Command’s Joint Force Space Component Command, through the Joint Space Operations Centre, indicates that Tiangong-2 has moved from an altitude of around 380 by 386 km down to 292 by 297 km.

No official announcement regarding the status of the Tiangong-2 space lab has been made by the China Manned Space Engineering Office (CMSE), however, China has made no secret of its plans to establish a permanent orbital presence over the Earth in the 2020s – and that to do so, they would discontinue operations with both Tiangong-1 and Tiangong-2. and de-orbit both.

Measuring 10.4 metres in length and some 3.3 metres in maximum diameter, Tiangong-2 weighs 8.6 metric tonnes – making it the same overall size and weight as Tiangong-1, launched in 2011. The re-entry of that unit came after a series of alarmist headlines claiming it would “crash” to Earth after it was reported the Chinese only had partial control over it. Because of that tabloid farrago, some have speculated the alteration in Tiangong-2’s orbit is to allow China to retain full control over the facility, including when it re-enters the atmosphere.

Jing Haipeng (l) and Chen dong (r) aboard Tiangong-2. The only crew to visit the facility Credit: CCTV

Launched in September 2016, Tiangong-2 hosted a single crewed visit that same year, which lasted 30 days. In 2017 served as a test-bed for verifying on-orbit automated docking and refuelling capabilities  – two aspects of operations vital to the Chinese ambitions of developing their large-scale space station – using the Tianzhou-1 cargo spacecraft.

Tiangong-2 carried a range of science payloads, including POLAR, a gamma-ray burst detector developed by an international collaboration including Swiss, Chinese and Polish institutes. According to principal investigator Nicolas Produit, this astro-particle experiment collected excellent data during six months of operations, with science results to be published shortly. It is the kind of international collaborative effort China would like to develop with its new station.

Artist’s impression of the planned Chinese space station complex. Credit: CCTV

China is aiming to launch the first module of the space station proper, named Tianhe, around 2020. This mission first requires the nominal return-to-flight of the heavy lift Long March 5 launch vehicle, which suffered a launch failure in July 2017. When completed, the space station will mass between 60 and 100 metric tonnes, including two experiment modules due for launch in 2022. It will be capable of hosting three astronauts in rotations of up to six months at a time. A further element of the station will be a free-flying Hubble-class space telescope capable of docking with the station to receive propellants and undergo maintenance and repairs.

More on Ceres and the Building Blocks of Life

In February 2017, I wrote about the discovery of the basic building blocks of life on Ceres, which has been the subject of the joint NASA / ESA Dawn mission since March 2015.

The discovery of aliphatic compounds on the surface of Ceres was made by an international team of scientists who had been reviewing data from the Visible and Infra-red Mapping Spectrometer (VIMS) aboard the spacecraft. Now, a new study conducted by a team of researchers from Brown University suggests that these patches contain more organic material than previously thought.

Dawn spacecraft data show a region around the Ernutet crater where organic concentrations have been discovered (labelled “a” through “f”). The colour coding shows the strength of the organics absorption band, with warmer colours indicating the highest concentrations. Credit: NASA/JPL / UCLA / ASI / INAF / MPS / DLR / IDA

Aliphatics are a type of compound where carbon atoms form open chains that are commonly bound with oxygen, nitrogen, sulphur and chlorine – all of which are necessary for the evolution of life. This doesn’t actually mean that Ceres supports life, because these molecules can also arise from non-biological processes. Nevertheless, the presence of these compounds does raise the questions.

The team behind original discovery of the aliphatics, found within a 1000 km² region around of the Ernutet crater, concluded that between 6 and 10% of the spectral signature detected on Ceres could be explained by organic matter. As hydrothermal activity had been detected on Ceres, the researchers hypothesised that the molecules were endogenous in origin – that is, they came from inside the protoplanet. Given that ammonia-bearing hydrated minerals, water ice, carbonates, and salts have also been detected on Ceres, there is the suggestion that it may have an interior environment that can support prebiotic chemistry.

Dawn mission (NASA / JPL) – click for full size

However, rather than relying on Earth rocks on which to base their work and findings, the team from Brown University used carbonaceous chondrite meteors, which have been shown to contain organic material that is slightly different from what we are familiar with here on Earth. As a result, they determined that the organics found on Ceres were distinct from their terrestrial counterparts – and the up to 40 to 50% of the spectral signal we see on Ceres is explained by organics – far more than originally estimated.

If this latter estimate is correct, it raises the question about where it came from – 40% is a lot for the compound to be entirely endogenous in origin. Rather, the high concentrations seem to be more consistent with being deposited by a comet impact.

Given that the asteroid belt is composed of material left over from the formation of the Solar System,  determining where these organics came from could shed light on how organic molecules were distributed throughout the Solar System early in its history, and the role this distribution may have played in the development of life here in Earth.

If, however, the compound deposits are endogenous in origin, there is still the question of what mechanisms were / are in play to result in such high concentrations emerged in Ceres’ northern hemisphere, and then preserve them in these locations. This is a question unlikely to be answered without follow-up missions able to obtain and analyse samples gathered from the surface of the protoplanet.

Continue reading “Space Sunday: stations, Ceres, doubts and rockets”