Tag Archives: Space and Astronomy

Space Sunday: clouds, sand, meteors and launches

Artist's impression of Akatsuki in orbit around Venus

Artist’s impression of Akatsuki in orbit around Venus

In my last Space Sunday update, I was writing at the very time a final effort was being made to see a little Japanese space probe finally achieve an operational orbit around Venus, precisely five years to the date after the first attempt failed as a result of the craft’s primary motor malfunctioning.

At the time of writing that update, it appeared as if little Akatsuki (“Dawn”), designed to probe the Venusian climate and atmosphere had finally arrived in orbit about the planet, but as I noted, final confirmation would take a while.  In the end, it wasn’t until Wednesday, December 9th that the Japan Aerospace eXploration Agency (JAXA) did confirm Akatsuki, less than a metre on a side (excluding its solar panels) was secure in its orbit around Venus and would likely be able to complete its mission.

Following the failure of its main engine on December 7th 2010 during a critical braking manoeuvre, the probe had finished up in a heliocentric orbit, circling the sun and heading away from Venus. However, orbital mechanics being as they are, both the probe and Venus would occupy the same part of space once again in December 2015, presenting final opportunity to push the probe into orbit using its RCS manoeuvring thrusters. This is precisely what happened on the night of December 6th / 7th, 2015. While not designed for this purpose, a set of the probe’s RCS thrusters undertook a 20-minute burn just before midnight UTC on December 6th, and preliminary telemetry received on Earth some 30+ minutes later showed Akatsuki had achieved sufficient braking to enter a very elliptical orbit around Venus.

A simple orbital diagram released as a part of the low-key JAXA press release confirming Akatsuki had arrived in orbit around Venus

A simple orbital diagram released as a part of the low-key JAXA press release confirming Akatsuki had arrived in orbit around Venus (image: JAXA)

Data received since then show that the craft is in an eccentric orbit with an apoasis altitude (the point at which it is furthest from the surface of Venus) of around 440,000km, and a periapsis altitude (the point at which it is closest to the surface of Venus) of around 400km. This is a considerably broader orbit than the mission had originally intended back in 2010, giving the vehicle an orbital period of around 13.5 days, the orbit slightly inclined relative to Venus’ equator.

An ultra-violet image of Venus, returned by Akatsuki shortly after achieving its initial orbit around the planet, and having passed through periapis, already heading away from the planet

An ultra-violet image of Venus, returned by Akatsuki shortly after achieving its initial orbit around the planet, having passed periapsis during the braking manoeuvre, to head away from the planet (image: JAXA)

In order to maximise the science return from the vehicle – which is now operating well in excess of its designed operational life – JAXA plan to use the next few months to gradually ease Akatsuki in an orbit which reduces both the apoasis distance from Venus, and bring down the orbital period to about 9 days.

These manoeuvres will likely be completed by April 2016, allowing the full science mission to finally commence.  This is aimed at learning more about the atmosphere and weather on Venus as well as confirm the presence of active volcanoes and thunder, and also to try to understand exactly why  Earth and Venus developed so differently from each other, despite being seen as sister planets in some regards.

Even so, right from its arrival in its initial orbit, Akatsuki has been flexing its muscles, testing its imaging systems and returning a number of preliminary pictures of Venus to Earth, such as the ultra-violet image shown above right, captured just after the craft finally achieved orbit.

Curiosity reaches Sea of Sand

NASA’s Mars Science Laboratory rover Curiosity has reached the edge of the major “sea” of sand dunes located on the flank of “Mount Sharp”. Dubbed the ““Bagnold Dunes” after British military engineer Ralph Bagnold, who pioneered the study of sand dune formation and motion, doing much to further the understanding of mineral movements and transport by wind action. Such studies are seen as an essential part of understanding how big a role the Marian wind played in depositing concentrations of minerals often associated with water across the planet, and by extension, the behaviour and disposition of liquid water across Mars.

Sand is not a new phenomenon for rovers on Mars to encounter – Curiosity, Opportunity and Spirit have all had dealings with it in the past; in fact Spirit’s mission as a rover came to an end in 2009, after it effectively got stuck in a “sand trap”. However, the “Bagnold Dunes” are very different to the sandy environs previously encountered by rovers; it is a huge “genuine” dune field where the sand hills can reach the height of 2-storey buildings and cover areas equivalent to an American football field.

The rippled surface of the first Martian sand dune ever studied up close. Captured by Curiosity's Mastcam on November 27th, 2015 (Sol 1,176 on Mars), the view is looking up the curved slope of "High Dune", revealing a rippled surface of sand sculpted by the wind. The Bagnold dunes" are "active", in that they are migrating down the slope of "Mount Sharp" at the rate of around one metre (39 inches) a year. The dunes are active, migrating up to about one yard or meter a year.

The rippled surface of the first Martian sand dune ever studied up close. Captured by Curiosity’s Mastcam on November 27th, 2015 (Sol 1,176 on Mars), looking up the curved slope of “High Dune” as it rises above Curiosity. The “Bagnold Dunes” are “active”, in that they are migrating down the slope of “Mount Sharp” at the rate of around one metre (39 inches) a year  (image: NASA / JPL)

So far, Curiosity has only probed the edge of the dune field around a sand hill originally dubbed “Dune 1”, and now called “High Dune”, using both its camera to image the region and its wheels to test the surface material prior to moving deeper into the sands. Wheel slippage is a genuine concern for the rover when moving on loose surfaces, as it can both overtax the motors and put the rover at risk of toppling over. Given this, and while there are no plans to attempt any ascent up the side of a dune, the mission team are taking things cautiously.

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Space Sunday: of rockets, moons, carbon and telescopes

Moments before touchdown: the Blue Origin propulsion module, having lobbed a New Shephard capsule on a sub-orbital flight, powers its way to a historic landing so it can be refurbished and re-used

November 23rd, 2015: moments before touchdown: the Blue Origin propulsion module, having lobbed a New Shephard capsule on a sub-orbital flight, powers its way to a historic landing so it can be refurbished and re-used (image: Blue Origin)

Blue Origin, the private space company founded by Amazon billionaire Jeff Bezos has become the first company to successfully launch a rocket into space – and return all elements of the vehicle to Earth for re-use.

The flight, carried out in West Texas, took place on Monday, November 23rd. It comprised the company’s New Shephard capsule, being flown in an uncrewed mode, and a single stage, recoverable booster is powered by an engine also developed by the company.

Unlike SpaceX, Orbital Sciences, Boeing and Sierra Nevada Space corporation, all of whom are directly pursuing rocket and space vehicle designs capable of orbital flight, Blue Origin is taking a more incremental approach, with efforts focused on the sub-orbital market “space tourism” market. The company is looking to build a cost-effective launch system capable of lifting small groups of paying passengers into space on ballistic “hops” which allow them to experience around 4-5 minutes of zero gravity before returning them to Earth.

The November 23rd flight saw the uncrewed New Shephard vehicle hoisted aloft by the booster system which reached a speed of Mach 3.72, sufficient for it to impart enough velocity to the capsule so that it could, following separation, continue upwards to an altitude of 100.5 kilometres (329,839 feet), before starting its descent back to the ground and parachuting to a safe landing.

April 25th: A camera aboard the propulsion module captures the rear of the New Shephard capsule moments after separation in the first test flight intended to recover both capsule and launcher - although the latter was in fact lost on that flight

April 25th: A camera aboard the propulsion module captures the rear of the New Shephard capsule moments after separation in the first test flight intended to recover both capsule and launcher – although the latter was in fact lost on that flight (image: Blue Origin)

Following capsule separation, however, the booster rocket Also made a control descent back to Earth, rather than being discarded and lost. The design of the booster – which Blue Origin call the “propulsion module” to differentiate to from a “simple” rocket – means it is semi-capable of aerodynamic free-fall, and won’t simply topple over and start tumbling back to Earth. At 6.5 kilometres (4 miles) above the ground, a set of eight drag brakes are deployed to slow the vehicle, with fins along the outside of the module allowing it to be steered. At 1.5 kilometres (just under 1 mile) above the landing pad, the unit’s motor reignites, further slowing it to a safe landing speed and allowing it to precisely manoeuvre itself onto the landing pad.

Highlights of the actual test flight, mixed with computer-generated scenes of the New Shephard capsule carrying a group of tourists on their sub-orbital hop was released by Blue Origin on November 25th.

One of the first to congratulate Blue Origin on their flight was Elon Musk, the man behind SpaceX, which is also pursuing the goal of building a reusable rocket system, but had yet to achieve a successful recovery of the first stage of their Falcon 9 booster. However, as Musk pointed out, there are significant differences and challenges involved in bringing a sub-orbital launch back to Earth and a booster  which has to reach far higher velocities in order to lob a payload into orbit, as SpaceX is already doing.

Not that Blue Origin doesn’t have orbital aspirations; both the “propulsion module” and New Shephard are designed to be integrated into a larger launch vehicle capable of placing the capsule into orbit.  The November 23rd flight itself marks the second attempt to launch and recover both New Shepard and the propulsion module; in April 2015, the first attempt succeeded in recovering the capsule, but a failure in the drag brake hydraulic system on the propulsion module resulted in its loss.

Martian Moon Starting Slow Breakup?

A Mercator map of Phobos showing the compex system of groves and potential lines of fracture across the little moon. Some of these, notably those located close to it, are thought to be the result of the impact which created Stickney crater (left of centre in the map); however most of them seem to be the first indications that Phobos is starting to slowly break-up

A Mercator map of Phobos showing the complex system of groves and potential lines of fracture across the little moon. Some of these, notably those located close to it, are thought to be the result of the impact which created Stickney crater (left of centre in the map); however most of them seem to be the first indications that Phobos is starting to slowly break-up (image: US Geological Survey)

Mars has two natural moons, Deimos and Phobos. Neither are particularly large; Deimos is only 15 × 12.2 × 11 km in size, and orbits Mars once every 30 hours;  Phobos measures just 27 × 22 × 18 km, and orbits the planet once every 7 hours and 39 minutes. Both exhibit interesting properties, in that Deimos is slowly moving away from Mars, and may even break from Mars’ influence in a few hundred million years.

Phobos, however is doing the reverse; it is gradually closing in on Mars at a rate of about 2 metres (6.6 ft) every 100 years. This means that over time, it is being exposed to greater and greater gravitational forces as it approaches its Roche limit.

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Space Sunday: metal rain and glass on Mars, HoloLens into orbit

Comet Siding Spring's passage through the solar system 2013-2014

Comet Siding Spring’s passage through the solar system 2014

In October 2014, I wrote about comet Sliding Spring and it’s close approach to Mars as it swung through the solar system.

The comet had been identified as coming from the Oort cloud (or the Öpik–Oort cloud, to give proper recognition both astronomers who initially and independently postulated its existence), a spherical cloud of debris left-over from the creation of the solar system, occupying a huge area starting some 2,000-5,000 AU (2,000 to 5,000 times the distance from the Earth to the Sun) and extending out to around 50-100,000 AU – or about one light year away.

There is nothing odd about comets from the Oort cloud per se, but Sliding Spring appeared to be making its very first journey into the inner solar system, and so astronomers were keen to try to study it as best they could. Given the close pass at Mars, the vehicles on and orbiting that planet stood to have something of a grandstand view of things – providing certain precautions were taken, as I noted at the time.

An artist's impression of MAVEN in orbit around Mars (NASA / JPL)

An artist’s impression of MAVEN in orbit around Mars

Now data released by NASA shows that the comet’s flight past Mars did result in something very unusual: the comet’s tail, which brushed the Martian atmosphere, resulted in a “rain of metal” over the planet.

The data was obtained by NASA’s Mars Atmosphere and Volatile EvolutioN Mission (MAVEN), which at the time of the comet’s passage was so recent an arrival at Mars, that all its instruments hadn’t been fully commissioned. Hence, in part, the delay in releasing the data – NASA wanted to be sure MAVEN was recording things accurately.

According to MAVEN, the direct detection of sodium, magnesium, aluminium, chromium, nickel, copper, zinc, iron and other metals high in the Martian atmosphere can be linked directly to material sloughing off of the comet as it passed.

“This must have been a mind-blowing meteor shower,” said Nick Schneider of the Laboratory of Atmospheric and Space Physics at the University of Colorado, commenting on the data returned by the orbiter. Such is the strength of the signal of magnesium and iron measurements, the hourly meteor rate overhead on Mars must have been tens of thousands of “shooting stars” per hour over a period of many hours.

An artist's impression of meteors resulting from comet Siding Spring in the sky over NASA's MSL Curiosity rover

An artist’s impression of meteors resulting from comet Siding Spring in the sky over NASA’s MSL Curiosity rover

“I’m not sure anyone alive has ever seen that,” Schneider added, “and the closest thing in human history might the the 1833 Leonids shower.” The metal ions were the remains of pebbles and other pieces shed from the comet that burned up, or “ablated” into individual atoms as they struck the Martian atmosphere at 56 kilometres per second (125,000 miles per hour).

What is particularly important about the event is that as scientists know the source of the dust particles, it’s speed, and key information about Mars’ upper atmosphere, it is possible to learn more about Mars’ ionosphere, the comet’s composition, and even the workings of Earth’s ionosphere when it is hit by comet or asteroid debris.

Impact Glass

There is glass on Mars, and it might just be the ideal place in which to find any evidence of past microbial life.

The type of glass in question is referred to as “impact glass”, and is formed as a result of the heat generated by the impact of a meteorite melts the surrounding rock into glass. when a meteorite strikes the surface of a planet or moon, melting the surrounding rock into glass, preserving and organic matter that existed on or in the rock prior to the meteorite impact occurring.

In 2014, a research team examining impact glass formed millions of years ago as a result of meteorite strikes in Antarctica form found organic molecules and plant matter within the glass. Their work spurred a group of planetary science graduates at Brown University, Rhode Island, to simulate the spectral composition of possible Martian impact glass by using chemicals, compounds and powders matching those known to compose the surface material on Mars, and then melting the mix at high temperatures to form glass, which they then subjected to spectrographic analysis.

The team then compared the results of their analysis with spectral analyses of the surface of Mars carried out by the Imaging Spectrometer aboard NASA’s Mars Reconnaissance Orbiter (MRO) – and found a very similar spectral signature in areas where such impact glass would be expected to form, such as around the central peaks of craters caused by meteorite impacts.

A spectrographic image of the central peak of the Alga Crater impact zone, taken by MRO. The green colours indicate the presence of impact glass

A spectrographic image of the central peak of the Alga Crater impact zone, taken by MRO. The green colours indicate the presence of impact glass

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Space Sunday: Philae, Titan and Pluto, oh my!

November 12th, 2015: Philae departs Rosetta en route for the surface of comet 67P/C-G

November 12th, 2015: Philae departs Rosetta en route for the surface of comet 67P/C-G  (image courtesy of ESA)

ESA’s Philae lander, which as I reported a week ago, resumed contact with Earth via its “Parent”, Rosetta, after seven months in hibernation, continues to return data to Earth from comet 67P/Churyumov–Gerasimenko (67P/C-G) as it continues towards the Sun.

Friday, June 19th, marked the latest transmission from Philae, which is about the size of a domestic washing machine, bringing the total of communications with mission control in Germany to 3 since the lander managed to re-establish its link with Rosetta.

Communications are sporadic because it is still not entirely clear where Philae is sitting on the comet, having bounced across the surface following its initial touch-down in November 2014. This, and Rosetta’s science-focused orbit around the comet means that there can be extended periods of several days between the times when both spacecraft and lander are suitably aligned to allow communications to take place.

The Friday communication lasted 19 minutes, and allowed the lander to return a further 185 packets of data to Earth. The data gave additional confirmation that Philae is in good health and in an environment which means it should be quite comfortable for a good while – thus increasing the chances of it resuming its science activities.

“Among other things, we have received updated status information,” Michael Maibaum, a systems engineer at the DLR Lander Control Centre in Cologne, reported following the Friday contact. “At present, the lander is operating at a temperature of zero degrees Celsius, which means that the battery is now warm enough to store energy. This means that Philae will also be able to work during the comet’s night, regardless of solar illumination.”

The three communications so far received mean that the mission team now have sufficient data to be able to more accurately position Rosetta so that it can continue with its primary science mission while being better placed to improve radio visibility between it and the lander’s estimated location. The first set of commands for the spacecraft to start adjusting its orbit were uploaded on Wednesday, June 17th, and and further set of instructions were uploaded on Saturday, June 20th. The aim is to close the distance between Rosetta and the comet to 177 kilometres within an orbit that will allow the orbiter to be above Philae’s horizon more regularly than is currently the case.

Pluto’s Gentle Fade In

NASA’s New Horizons mission to the Pluto-Charon system is now less than a month from its point of closest approach, which will occur on July 14th, 2015. As the fast-moving spacecraft closes on the two planetoids, the images it is returning to Earth of Pluto are starting to show tantalising splotches of dark across the planetoid’s surface, the first hints of landforms.

Pluto slowly starts to unmask itself as New horizons approaches

Pluto slowly starts to unmask itself as New horizons approaches (image: NASA / APL)

The pictures are still nowhere near being as clear as they should be in the days immediately prior to and following the point of closest approach, but they are still nevertheless interesting; in April 2015, New Horizons images what appears to be a polar ice cap on Pluto, so scientists are curious to what else might be revealed.

At the time of closest approach, New Horizons should be within 10,000 kilometres (6,200 miles) of Pluto and around 27,000 kilometres (17,000 miles) of Charon. The fly-by of Pluto should allow the main telescope camera system on the vehicle to take selected high-resolution images of Pluto at a scale of 50 metres / pixel. It is hoped that the average resolution of daylight images captured of Pluto will be around 1.6 km (1 mile) resolution, and will allow the composition of 4-colour maps of the surface.

From around 3.2 days before closest approach, long-range imaging will be used to map both worlds to a resolution of around 40 kilometres (25 miles).  New Horizons will also attempt to gather data on the nature of any atmosphere present on Pluto and seek evidence of any cryovolcanism which might be occurring or surface feature changes which might be attributable to snowfall or similar.

Titan: Even More In Common

An infographic released by NASA in June 2014 to mark Cassni's ten years in operation around Saturn

An infographic released by NASA in June 2014 to mark Cassni’s ten years in operation around Saturn – click for full size (NASA)

There are only two places in our solar system known of have rainfall, rivers and oceans, as well as a thick atmosphere, rocky ground and plate tectonics. They are Earth and Saturn’s huge moon, Titan. Now the joint ESA / NASA Cassini mission has revealed Titan shares something else with Earth: polar “winds” that suck gasses out of its atmosphere and into space.

Titan’s atmosphere has around a 50% higher surface pressure than Earth’s, and is comprised mainly of nitrogen and methane, and is rich in hydrocarbons, which also exist in lakes, reivers and seas on the surface of the planet.

Several years ago Cassini, which has been orbiting in orbit around Saturn for over a decade, revealed that around seven tonnes of hydrocarbons and nitriles were being lost every day from the upper layers of Titan’s atmosphere, but the mechanism causing the loss remained unknown until CAPS, the instrument which first recorded the loss recorded the “wind” in action.

Essentially, sunlight striking the upper layers of Titan’s atmosphere ejects negatively charged electrons out of the hydrocarbon and nitrile molecules resting there. These electrons are then drawn away along Saturn’s magnetic field, generating their own electrical field strong enough to “pull” the positively charged particles left behind by the formation of the original electrons out of the atmosphere along with them.

On Earth, this process charges particles in the atmosphere and draws them up along the planet’s magnetic field, where they can escape at the poles, and the same thing is happening on Titan. The discovery has lead to speculation that similar processes might be at work on Mars and Venus.

In this false-colour image, lakes and

In this false-colour image, lakes and “sea” of hydrocarbons can be seen scattered across the north polar region of Titan (the white areas indicate parts of the moon’s surface which had not been imaged at the time this mosaic was constructed (image: NASA)

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