Space Sunday: ExoMars, a magic movie and a “forbidden planet”

A model of the ExoMars rover, Rosalind Franklin, in the ROCC Mars Yard. Credit: ESA

When it comes to Mars rover missions, eyes tend to be firmly on NASA’s Mars Science Laboratory Curiosity vehicle and the upcoming Mars 2020 rover.

However, if all goes according to plan, come 2021, Curosity and Mars 2020 will have a smaller European cousin trundling around Mars with them, thanks to the arrival of ExoMars rover Rosalind Franklin. While the rover isn’t due to be launched for just over 12 months, the European Space Agency (ESA) take two further steps towards the mission in June 2019.

At the start of the month, ESA inaugurated the Rover Operations Control Centre (ROCC) in Turin, Italy. Designed to be the hub that orchestrates all operational elements supporting Rosalind Franklin once it has been delivered to the surface of Mars by its Russian-built landing platform, ROCC is one of the most advanced mission operations centres in the world.

This is the crucial place on Earth from where we will listen to the rover’s instruments, see what she sees and send commands to direct the search for evidence of life on and under the surface.

– Jan Wörner, ESA’s Director General

As well as providing communications with the rover, data processing, and science and engineering support, the ROCC boasts one of the largest “Mars Yard” sandboxes currently available. Filled with 140 tonnes of Martian analogue soil, it offer a range of simulated terrains similar to those the rover might encounter within its proposed landing site. Such simulation capabilities will allow Earth-based teams to carry out a wide range of activities  using the rover’s Earth-bound twin before committing to particular courses of action, or to help assist the rover should it get into difficulties on Mars.

Use of such environments is not new; NASA uses an assortment of indoor and outdoor Mars Yards to help support their static and rover surface operations on Mars. However, the ROCC Mars Yard is somewhat unique in its capabilities.

For example, as ExoMars has a drilling system designed to reach up to 2 metres (6 ft) below the Martian surface, the ROCC Mars Yard includes a “well” that allows rover operators to exercise the full sequence of collecting Martian samples from well below the Martian surface. This well can be filled with different types / densities of material, so if the Rosalind Franklin gets into difficulties in operating its drill, engineers can attempt to replicate the exact conditions and work out how best to resolve problems.

The “well” in the ROCC Mars Yard, as seen from underneath, allowing the ExoMars rover mission team rehearse the full range of sample gathering operations. Credit: ESA

And while it is not part of the main Mars Yard, ROCC rover operations will be assisted by a second simulation centre in Zurich, Switzerland. This 64-metre square platform can be filled with 20 tonnes of simulated Martian surface materials and inclined up to 30-degrees. Engineers can then use another rover analogue to see how the rover might – or might not – be able to negotiate slopes.

For example, what might happen if the Rosalind Franklin tries to ascend / descend a slope covered in loose material? What are the risks of soil slippage that might result in a loss of the rover’s ability to steer itself? What are the risks of the surface material shifting sufficiently enough that the rover might topple over? What’s the best way to tackle the incline? The test rig in Zurich is intended to answer questions like these ahead of committing the Mars rover to a course of action. In fact, it has already played a crucial role in helping to develop the rover’s unique wheels.

Both the Mars Yard and the Zurich facility will be used throughout the rover’s surface mission on Mars, right from the initial deployment of the rover from its Russian landing platform (called Kazachok, meaning “little Cossack”).

With the Mars yard next to mission control, operators can gain experience working with autonomous navigation and see the whole picture when it comes to operating a rover on Mars. Besides training and operations, this fit-for-purpose centre is ideal for trouble shooting.

– Luc Joudrier, ExoMars Rover Operations Manager

The Mars Yard can also simulate the normal daytime lighting conditions on Mars. Credit: ESA

June will see the new centre commence a series of full-scale simulations designed to help staff familiarise themselves the centre’s capabilities before commencing full-scale rehearsals for  the rover’s arrival on Mars in March 2021.

Meanwhile, in the UK – which carries responsibility for assembling the rover – Rosalind Franklin is coming together. The drill and a key set of scientific instruments—the Analytical Laboratory Drawer—have both been declared fit for Mars and integrated into the rover’s body. Next up is the rover’s eyes – the panoramic camera systems. Once integration in the UK has been completed, the rover will be transported to Toulouse, France, where it will be put through a range of tests to simulate its time in space en route to Mars and the conditions its systems will be exposed to on the surface of Mars.

The targeted landing site for Rosalind Franklin is Oxia Planum, a region that preserves a rich record of geological history from the planet’s wetter past. With an elevation more than 3000 m below the Martian mean, it contains one of the largest exposures of clay-bearing rocks that are around 3.9 billion years old. The site sits in an area of valley systems with the exposed rocks exhibiting different compositions, indicating a variety of deposition and wetting environments, marking it as an ideal candidate for the rover to achieve its mission goals.

Oxia Planum – Location Map. Credit: NASA

However, the landing zone is well outside the current orbital range of the other half of the ExoMars mission, the Trace Gas Orbiter (TGO). This arrived in Mars orbit in late 2016 with a primary mission to probe the Martian atmosphere, identify water abundance within the planet and study its surface. however, TGO is also intended to be a communications relay for Rosalind Franklin.

In order to do this, TGO must substantially alter its current 2-hour orbit of Mars.This could be done nearer the time of the rover’s arrival on Mars – but would require extensive use of the orbiter’s fuel reserves. Instead, engineers are going to allow orbital mechanics do the work for them, with just a little help from TGO’s motors.

All satellites orbiting a planet tend to wobble a little as they do so, and slowly drift from their intended orbit – hence when they have small gas thrusters to help them maintain an orbit that follows their desired track around a planet. On June 15th, 2019, TGO will perform an Inclination Change Manoeuvre (ICO), firing its motor very briefly to nudge itself into a new orbital inclination. After this, orbital mechanics will take over, and, coupled with the change in TGO’s orbital velocity following the engine burn, the satellite will, over the next two years slowly shift its orbit around Mars so that come March 2021, it will be in precisely the right position to monitor the ExoMars lander’s Entry, Descent and Landing (EDL) mission phase, and afterwards act as a communications relay for the rover.

Left: the red line shows TGO’s orbit on Mars today. The black line represents its orbital path in 2021, which it will reach over the next 2 years and with minimal fuel expenditure. The green line indicates Rosalind Franklin’s approach to Mars. Right: blue dots along the orbits of TGO and Rosalind Franklin’s path show how the former will monitor the latter’s EDL in March 2021. Credit ESA

This entire process will be achieved using minimal fuel reserves and allow TGO to continue its science mission uninterrupted. Then, just ahead of Rosalind Franklin’s arrival at Mars, TGO will perform another small engine burn to ensure it is “in phase” with the lander’s approach – that is, on the same side of Mars as the lander – allowing it to both monitor the lander’s EDL and take up its role as communications relay with Earth.

A Most Remarkable Movie

John Nevil Maskelyne, via Wikipedia

The first film ever made of a total solar eclipse has been restored by specialists at the British Film Institute (BFI) and made available for viewing.

Recorded during the May 1900 by Englishman John Nevil Maskelyne (1839-1917) during a Royal Astronomical Society (RAS) expedition to North Carolina, America, the film has been part of the RAS archives for over a century. However, a team from the BFI were brought in to try to preserve the film before the original might deteriorate. They scanned the original footage frame-by-frame, flicker, scratches and all, to produce a high-resolution 4K copy.

The film actually represents Maskelyne’s second attempt to capture a total solar eclipse. In 1898, he travelled to India to photograph an eclipse – only to have the film stolen. For the 1900 expedition to North America, he built a special telescopic adapter for his camera – becoming one of the first in the world to do so.

Maskelyne himself was an unusual character. A professional magician, and member of The Magic Circle, he was the founding father of a magical dynasty, and even has a magic award named for him. In addition, he founded Occult Committee, working to expose charlatans claiming paranormal powers. However, he was also fascinated by astronomy, and joined the Royal Astronomical Society just it was formally recognising the newly-formed field of astro-photography. Already fascinated by photography as a means to add a little more theatre to magic shows, Maskelyne was an immediate convert to this new science.

As a record of a solar eclipse, Maskelyne’s film is a magical piece itself, as Dr. Joshua Nall, Chair of the RAS’s Astronomical Heritage Committee noted in a press release on the restoration:

This is a wonderful archival discovery: perhaps the oldest surviving astronomical film, it is a really striking record of both early cinema and late Victorian eclipse observing.

Bryony Dixon, silent film curator at the BFI added:

Film, like magic combines both art and science. This is a story about magic; magic and art and science and film and the blurred lines between them. Early film historians have been looking for this film for many years. Like one of his elaborate illusions, it’s exciting to think that this only known surviving film by Maskelyne, has reappeared now.

Discovering the Forbidden Planet

We’ve discovered enough exoplanets over the last few decades to make it seem almost like an everyday occurrence. But the recently discovered NGTS-4b is a little different. At about three times the size of Earth, or 20% the size of Neptune, it sits within the range of exoplanets called “mini Neptunes”. But that isn’t what makes NGTS-4b different.

It’s also a super-hot planet, with a surface temperature estimated to be 1,000-degrees Celsius – hotter than the surface of any planet in the solar system, which makes it interesting, but it’s also not what makes it different.

An artist’s impression of how NGTS-4b might look in comparison to its parent star. Credit: University of Warwick/Mark Garlick

What makes NGTS-4b different is the fact that it has been discovered exactly where it has no right to be: within the Neptunian Desert region of its parent star, an M-class red dwarf star 920 light-years from Earth.

The “Neptunian Desert” is a region believed to exist around all stars where the force of radiation flowing out from the star would strip away the atmosphere from any planet orbiting within it. And since planets of Neptune’s size or larger are predominantly gas, with only a relatively small solid core, then they simply should not be able to exist within this zone and retain their atmospheres. Yet it appears NGTS-4b has done precisely that, marking it as the first planet of its size to ever be discovered within the Neptunian Desert of a star, earning itself the nickname The Forbidden Planet.

The planet was discovered by astronomers at the University of Warwick in the UK using data from the Next Generation Transit Survey facility, located at Paranal Observatory in the Atacama desert in Chile. A robotic system using a mini-array of 20-cm (8-in) telescopes, NGTS is designed to discover super-Earths and exo-Neptunes transiting relatively bright and nearby stars.

Starting operations in 2015, NGTS made its first confirmed discovery, a hot Jupiter-sized extrasolar planet orbiting a red dwarf star roughly 600 light years away, in 2017. That discovery also altered thinking about where large planets might exist; until NGTS-1b, it had been thought M-class dwarf stars were incapable for supporting such large planetary bodies.

The 12 20cm telescopes of the NGTS array and members of the operating staff of the European Southern Observatory (ESO), Chile. The ESO Very Large Telescope can be seen on the hill in the distance. Credit: G. Lambert

The Forbidden Planet, however is something else entirely. Not only has it retained it’s atmosphere, it is so close to its parent, it zips around it every 1.3 terrestrial days.

The NTGS facility identifies potential exoplanets by looking for regular dips in the apparent brightness of another star. Such regular dips are generally caused by a planet “transiting” the star – that is, passing in front of the star when observed from Earth. Up until now, ground-based instruments have only been able to detect transiting planets that cause at least a 1% drop in their parent star’s apparent brightness. However, The Forbidden Planet only causes a 0.2% dip, marking it as the first planet causing so small a dip to ever be discovered using ground-based instruments. Even so, it took a year of study to confirm the period dips in NGTS-4’s brightness were the result of a relatively large, fast-moving planet travelling around it.

Now astronomers are trying to figure out just how The Forbidden Planet has managed to retain its atmosphere despite its location. Two theories have thus far gained the most support. The first is that the planet actually formed much further out from its parent, but has slowly migrated inwards, perhaps only entering the Neptunian Desert around its parent about a million years ago. This would mean the planet is just at the start of the process of solar energy ripping its atmosphere away.

The second is that the planet was once actually, much, much larger in terms of its atmosphere, and we’ve detected it at a time when its atmosphere is still being stripped away, but has enough remnants left for us to be able to detect it.

Whatever the reason, NGTS-4b is causing some serious re-thinking about exoplanets and their possible locations, and the international team behind NGTS is now going back through the data already gathered to see if they may have missed other planets lying within the Neptunian Desert region of other stars the facility has observed, simply because they thought none could exist within this region.