Space Sunday: images of Mars, comets and giant planets

Looking across Gale Crater as it might appear from NASA’s Mars Science Laboratory rover Curiosity. Render created by Kevin M Gill.

Kevin M. Gill is a software engineer, planetary and climate data wrangler at NASA’s Jet Propulsion Laboratory. He’s been working with digital terrain models and ortho images from the HiRISE imaging system aboard NASA’s Mars  Reconnaissance Orbiter (MRO) to create some stunning computer models and images of Endeavour and Gale craters, where the Opportunity and Curiosity rovers are exploring, as well as other regions of Mars. These have caused a stir on social media this week, and rightly so.

Kevin provides a detailed description of how he produces the images, which involves a range of software tools including ImageMagick, Maya and Photoshop. For those interested in creating computer renderings, his post makes a fascinating read; for those who love images of Mars, his images offer a stunning new perspective on the planet. The images utilise a slight vertical height exaggeration and false colour / lighting adjusted to Earth daylight standards, but the results are undeniably stunning.

A view along a volcanic fissure in the Cerberus Palas region of Mars. Rendering by Kevin M. Gill

Some of the images offer a unique perspective on surface features, such as the one above, showing a volcanic fissure in Cerberus Palas in the north-eastern Elysium quadrangle of Mars.

For those interested in producing vistas of Mars in a platform such as Linden Lab’s Sansar, Kevin’s work and notes could offer a starting point. In turn, Sansar could offer the perfect VR visualisation platform for allowing people to “visit” and learn about Mars.

“Mount Sharp” (Aeolis Mons), the mound of material deposited against the central impact peak of Gale Crater. Render by Kevin M Gill.

Meanwhile, the MSL team are moving closer to resuming drilling operations with the Curiosity rover.

These were suspended in December 2016. Prior to that, Curiosity had used the drill system mounted on its robot arm a total of 15 times between 2013 and 2016. On each of those occasions, two contact post, one either side of the bit, were placed on the target rock before the bit was extended by the drill feed mechanism, helping to gauge and support the drill. It was reliability issues with the feed mechanism which led to the suspension of all drilling operations.

Engineers have been investigating ways to use the drill without any reliance on the feed mechanism. This requires the drill to remain extended, the rover’s arm bringing it directly in contact with the rock to be drilled, without any support from the stabilising arms. In order for this to work, it is essential the drill bit  – which not only cuts into rocks, but gathers samples from within them – can be placed with minimal downward or side-to-side pressure or motion on it, to ensure it is not damaged or becomes stuck.

The issue here is that when supported by the stabilisers, the drill had only one axis of movement, without them, it could be subject to fix degree freedom of movement as vibrations from the drilling process feed back into the rover’s arm. To minimise this risk, tests are being carried out to determine if sensors in the robot arm are sensitive enough to detect potentially damaging motions in the drill when in use, and shut down the drilling operation.

On October 17th, 2017, NASA conducted the first test with Curiosity’s robot arm aimed at resuming the rover’s ability to gather rock samples with the drill mounted on the arm. Credit: NASA/JPL

To this end, on October 17th, 2017, Curiosity was commanded to place the drill bit in contact with a rock for the first time in ten months and without the use of the stabilisers. The bit was then gently pressed downward and moved slightly from side-to-side to see how well the sensors responded, the idea being that when the drill resumes operations, the sensors can be used to automatically detect potentially harmful movements in the drill head which could result in the bit being damage or becoming stuck.

It’s still likely to be several months before Curiosity resumes drilling operations, with further tests in the planning. However, mission managers are optimistic the rover will at some point be able to resume use the drill to gather samples from within rocks for analysis.

Deep Space Gateway Gains Momentum

On November 1st, 2017, NASA awarded contracts to five companies to examine how they can develop a power and propulsion module as the initial element of the agency’s proposed Deep Space Gateway.

As currently envisioned, the power and propulsion module will generate electrical power for the gateway, provide a communications relay and use a solar electric engine for manoeuvring the station in cislunar space. NASA had been examining their own ideas for the module, but it is hoped that the contracts will allow industry the chance to present their own ideas and technologies in support of the module’s development.

Part of the NASA studies involve the use of a 50-kilowatt solar electric propulsion (SEP) motor for the module, the idea being that if successful, the system could be scaled-up for use on missions to Mars.  While SEP systems can’t generate much thrust, they can run for long periods and are far more efficient than chemical systems.

Artist’s concept of the Deep Space Gateway passing close to the Moon. Credit: NASA

NASA had planned to test the SEP concept on the robotic portion of the now-cancelled Asteroid Redirect Mission (ARM), in which a robotic spacecraft would obtain a boulder-sized sample of a near Earth asteroid and return it to cislunar space for examination by astronauts. With the cancellation of that mission, the SEP programme has been in limbo; so issuing the contracts might both help revive the SEP project and allow commercial organisations weigh-in on the work.

These contracts are separate from those issued in 2016 to examine development of habitat modules for the gateway. However, all five of the companies that received contracts for Power and Propulsion Element studies also either have a habitat award or are partnered with a company that does.

How NASA plans to proceed with development of the station, including how it procures it from industry, will depend on the outcome of the studies as well as NASA’s overall exploration planning. At this point in time – and despite the October 5th, 2017 directive from the inaugural meeting of the re-invoked US National Space Council (NSC) concerning an American return to the Moon – the Deep Space Gateway remains a concept, not a formal NASA programme.

Also interested in participating in the programme is the European Space Agency. They are hoping to have a dedicated module forming part of the station, and are offering to develop a resupply system potentially capable of delivering up to nine tonnes of supplies to the Gateway.

The resupply vehicle would likely use the Ariane 6 launcher and solar electric propulsion system, rated around 60 kilowatts. ESA representatives believe the system could be ready for operation in 2025 or 2026, which fits with the time frame for the station’s development – which could see the power and propulsion module launched in 2022, as part of NASA’s Exploration Mission 2 mission for the Orion / Space Launch System. In the meantime, the first launch of the Ariane 6 booster is currently scheduled for 2020.

Exocomets Found 800 Light Years Away

In my previous Space Sunday article, I wrote about an extra-solar comet moving through the inner solar system. However, a team of astronomers have been using one of the two methods most commonly used to detect exoplanets, Transit Photometery, which requires monitoring stars for periodic dips in their brightness due to a planet transiting in front of the star, and found something much smaller orbiting a star.

According to a new study published by the research team, the remains of six exocomets have been observed orbiting around KIC 3542116, a spectral type F2V star located 800 light years from Earth. These comets are the smallest objects to date detecting the Transit Photometry method, and were detected as a result of their tails dimming the light of the star.

An artist’s impression of a swarm comet fragments around Tabby’s Star. Now it appears the first such exocomet fragments have been discovered around a star 800 light-years away. Credit: NASA

This marks the first time that Transit Photometry has been used to detect objects as small as comets – no easy task given the comet tails only obscure only about a tenth of 1% of the star’s light. Credit for the original detection goes to Thomas Jacobs, an astrophysicist and amateur astronomer and a member of Planet Hunters,  the citizen scientist project established to allow amateur astronomers access the data from the Kepler Space Telescope in the hopes that they would notice things that computer algorithms used to assess the data for possible exoplanets might miss.

While studying the first four years of data from Kepler, he found three sets of data for KIC 3542116 which didn’t correspond with data for planetary bodies orbiting the star. He contacted colleagues, and over the course of three months of investigation, they noted the asymmetry in the three light curves resembled those of disintegrated planets, which they had observed before – but the faintness of the dimming of the star’s light in each case suggested the objects responsible were a lot smaller than disintegrated planets.

This lead the team to conclude the data related to comets, each one possibly comparable in size to Halley’s Comet, which had passed within their Roche limits in relation to the star and disintegrated, leaving dust trails travelling at around 170,000 km/h (106,250 mph) orbiting the star. During their analysis, the researcher found three more matching sets of data, suggesting six comets had broken up in the star’s recent past.

That six comets – or their remnants – have been discovered in one star system raises some interesting questions. We know, for example, that the solar system experienced a period of intense comet activity (the Late Heavy Bombardment or LHB), which is thought to have been responsible for the distribution of water to Earth and the other terrestrial planets. KIC 3542116 is a yellow-white F2V star, between 1 and 1.4 times as massive as the Sun. Given this, it is possible that it is experiencing an event similar to the LHB. Watching it unfold could therefore tell us much about how similar activity influenced the evolution of our Solar System billions of years ago.

New Exoplanet Challenges Formation Theory

In theory it shouldn’t exist, a massive planet orbiting a tiny star. The planet, a so-called “hot Jupiter” is at least the size of our own Jupiter, but with about 20% less mass. It is orbiting a M-class red dwarf star with a radius and mass roughly half that of our own Sun.

The planet is the first discovery by the Next-Generation Transit Survey (or “NGTS’), an array of 12 telescopes which observe stars for detectable dips in the infra-red light they give off, and which might indicate the presence of an orbiting planet. Whilst observing the star in question, designated NGTS-1, which is some 600 light years away, the team using the array noticed the star’s brightness would dip every 2.6 terrestrial days. This put the planet very close to its parent star – around only 3% of the distance between the Earth and the Sun, or about 4.5 million km (2.8 million mi).

An artist’s impression of NGTS-1b orbiting its parent star. Credit: University of Warwick / Mark Garlick

According to current theories of planetary formation, such a huge planet should not be able to form around such a small star because the latter shouldn’t have enough material in its accretion disk to allow such a massive planet to form. Instead, such stars could only have smaller, solid planets similar in size to Earth forming.

Dr Daniel Bayliss, lead author of the study and from the University of Warwick, UK, commented, “The discovery of NGTS-1b was a complete surprise to us; such massive planets were not thought to exist around such small stars. Importantly, our challenge now is to find out how common these types of planets are in the galaxy, and with the new Next-Generation Transit Survey facility we are well-placed to do just that.”

NGTS is situated at the European Southern Observatory’s Paranal Observatory in the heart of the Atacama Desert, Chile, but is one of very few facilities to be run by external parties: Warwick, Leicester, Cambridge and Queen’s University, Belfast in the UK are involved, together with Observatoire de Genève, DLR Berlin and Universidad de Chile.

Professor Peter Wheatley leads NGTS, and was pleased to see these exciting results: “Having worked for almost a decade to develop the NGTS telescope array, it is thrilling to see it picking out new and unexpected types of planets. I’m looking forward to seeing what other kinds of exciting new planets we can turn up.

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