Space Sunday: rockets, water, wind and transits

 

For the second time in less than a month, SpaceX has landed the first stage of a Falcon 9 rocket on a platform at sea, bringing the total of successful landings the company has so far achieved to three.

The landing came at 05:30 GMT on the morning of Friday, May 6th, just nine minutes after the rocket had lifted-off from Cape Canaveral Air Force Station in Florida on a successful mission to carry the Japanese communications satellite JCSAT-14 to orbit.

Following separation, the first stage of the Falcon 9 1a rocket performed a series of flight manoeuvres referred to as “boost back”, which culminated in the first stage making a successful touch-down on the deck of the drone ship Of Course I Still Love You, the same craft used to recover the first stage of the Falcon 9 rocket to lift the CRS-8 resupply mission to a safe rendezvous with the International Space Station in April.

The recovery of the booster stage was actually an unexpected event – SpaceX had believed that the nature of the mission would more than likely result in a failure to achieve a successful landing.

“Given this mission’s GTO [Geostationary Transfer Orbit) destination, the first stage will be subject to extreme velocities and re-entry heating, making a successful landing unlikely,” SpaceX representatives stated ahead of the launch.

The Falcon 9 1a first stage secured on the deck of Of Course I Still Love You, following the successful May 6th landing

The Falcon 9 1a first stage secured on the deck of Of Course I Still Love You, following the successful May 6th landing. Credit: SpaceX

Ideally, the company would like to bring all of its boosters back to a touch-down on land, as was the case with their first successful landing in December 2015. However, some mission profiles mean that the Falcon 9 cannot carry sufficient fuel reserves to complete a set of “boost back” manoeuvres that would be enough for it to make landfall, so some landings at sea are inevitable if SpaceX is to get anywhere close to recovering the majority of its launchers.

Nevertheless, with three successful landings under its belt, and three first stage rockets requiring refurbishment in order to be able to fly again, SPaceX boss Elon Musk jokingly conceded, in a Tweet made after the landing, “May need to increase size of rocket storage hangar!”

The “Boiling” Waters of Mars

An international team from  France, the UK and the USA have produced the strongest evidence yet that the distinctive recurring slope lineae (RSL) features seen on the slopes of Martian craters are produced by liquid water. And not just any water; the study suggests the water is “boiling”.

RSLs have been the subject of intense debate and discussion since 2011; in essence, they are ridges and rills which appear on the slopes of hills and craters, notably in the equatorial regions of Mars during the summertime. The significance here being that on Earth, identical features are always the result of free-flowing water. As the “recurring” in the title suggests, the Martian RSLs appear to be active – frequently renewing themselves on a seasonal basis, with new RSLs sometimes also appearing at the same time.

Two images showing the flank of the same crater, revealing what appear to be active RSL, periodically renewed during the Martian summer

Two images showing the flank of the same crater, revealing what appear to be active RSL, periodically renewed during the Martian summer. Credit: NASA/JPL

However, the low pressure of Mars’ atmosphere means that water cannot survive long on the surface unprotected: it will either freeze or sublimate. So the idea of it surviving long enough to create trails in the sides of craters had many scientists scratching their heads. Then, in 2015, a NASA study put forward evidence RSLs might actually be the result of water containing a strong suspension of mineral salts – magnesium perchlorate, magnesium chlorate and sodium perchlorate. Such minerals could be sufficient enough to prevent water exposed to the surface environment on Mars either immediately freezing or sublimating.

Building on this idea, the French-led international team used blocks of water ice containing the same minerals and placed them on the slope of a simulated Martian crater housed inside a special Mars Chamber at the Open University in the UK. When the pressure in the chamber was reduced to the ambient surface pressure on Mars and the temperature adjusted to a typical Martian summer’s day, the team found the ice would melt, producing a liquid mix which effectively “boiled” filtering into the sand and moving down-slope. As it did so. the resultant vapour “blasted” sand grains upwards, creating ridges which would collapse onto themselves when they became too steep, forming channels almost identical in form to Martian RSLs.

The Mars Chamber at the Open University, UK, where the experiments were carried out

The Mars Chamber at the Open University, UK, where the experiments were carried out. Credit: The Open University

However, while the new study may further point the way towards water being present under the Martian surface and responsible for RSLs, it may also point to there being far less water on Mars outside of the frozen aquifers which have so far been possibly identified. Simply put, because of the “boiling water effect” of the lower atmospheric pressure on Mars, much less water is required to create the RSLs, so it might be that the subsurface pools from which they originate may be very small – possibly too small for them for support any form of Martian microbial life which might otherwise arise in such relative warm, wet environments.

Pluto has “Planet-like” Interaction with Solar Wind

new-horizon

An artist’s impression of New Horizons passing Pluto in July 2015. Credit: NASA

Pluto behaves less like a comet than expected and somewhat more like a planet like Earth, Mars or Venus in the way it interacts with the solar wind, the continuous outward flow of charged particles from the sun.

That’s the initial findings from the Solar Wind Around Pluto (SWAP) instrument aboard NASA’s New Horizons space vehicle, which performed a fly through of the  Pluto system in 2015, reaching its closest point to the little planet on July 14th, 2015.

The data from  SWAP has, for the first time, allowed scientists to observe how material coming off of Pluto’s atmosphere interacts with the solar wind. And it has led to another “Pluto surprise.”

“This is a type of interaction we’ve never seen before anywhere in our solar system,” said David J. McComas, professor of astrophysical sciences at Princeton University, and principal investigator for the SWAP instrument. “The results are astonishing.”

The solar wind plasma passes outwards from the Sun at around 160 million kilometres (100 million miles) per hour, washing a sea of protons and electrons through the solar system. Prior to SWAP’s findings, it had been thought that the interaction of this wind with Pluto would be much like it behaves around comets and other small bodies in the solar system.

These have a large region before them where the solar wind gently slows to flow around them, whereas larger planetary bodies abruptly divert the solar wind around them, often creating a long tail of heavy ions in their shadow. Pluto, however, seems to sit between the two in the way it interacts with the solar wind, although it has a bias towards the planetary model – including having the long tail of heavy ions streaming away from the Sun “behind” the planet, for about 118,00 km (73,800 mi)

Four images from New Horizons’ Long Range Reconnaissance Imager (LORRI) were combined with color data from the Ralph instrument to create this global view of Pluto. The images, taken when the spacecraft was 280,000 miles (450,000 kilometers) away from Pluto, show features as small as 1.4 miles (2.2 kilometers). Credits: NASA/JHUAPL/SwRI

Four images from New Horizons’ Long Range Reconnaissance Imager (LORRI) were combined with colour data from the Ralph instrument to create this global view of Pluto. The images, taken when the spacecraft was 450,000 km (280,000 mi) away from Pluto, show features as small as 2.2 km (1.4 mi) Credit: NASA / JHU/APL / SwRI

It had been thought that in being so far from the Sun – an average of 6 billion km (3.7 billion mi) – and being so small, Pluto would not have sufficient gravitational attraction to have a significant impact on the solar wind – much less hold onto heavy ions in its extended atmosphere. SWAP has revealed otherwise, confounding scientists’ expectations. Now thinking caps are on as to why it should be this way.

ExoMars Lander: Not Before 2020

Following the successful launch of the ExoMars orbiter mission on March 14th, the European Space Agency has now officially confirmed that the second part of the mission – a rover vehicle and science platform – will now miss its earliest launch date, targeted for the 2018 opposition. Instead, 2020 is now the likely launch period for the mission.

The delay had been expected; while the rover has been on track for a 2018 launch, a number of the science packages intended for the science platform have been running behind their development schedules, and it has become increasingly clear they would not be ready for a 2018 launch.

"Bridget" the ExoMars text vehicle, undergoing tests at the "Mars Cave" at

“Bridget” the ExoMars rover test vehicle, in the “Mars Cave” at Airbus Defence and Space in Stevenage, UK. Two rover forms one part of the ExoMars 2020 mission. Credit: UK Space Agency

The decision to delay, although not unexpected, does places a further financial burden on the mission. As such it must be referred back to the governments of the participating nations for them to consider the additional funding. The results of these deliberations are unlikely to be concluded before the December meeting of ESA government space ministers.

The rover, which is being developed in the UK by Airbus Defence and Space, weighs some 300 kilogrammes and is designed to directly seek out evidence of current or past microbial life on Mars, and is capable of drilling up to 2 metres beneath the Mars surface.

The 828-kilogramme surface science platform, which will also be the rover’s landing platform, is being built by the Russian space agency and is intended to carry a mix of Russian and European science packages. Once on Mars, the it is expected to operate for one Earth year, observing the climate, atmosphere, and radiation environment.

Transit of Mercury

On May 9th, 2016 Mercury will move across the face of the sun, offering a rare viewing opportunity for professional astronomers and backyard sky watchers alike.

As Mercury and Venus both orbit between Earth and the Sun, they both periodically pass directly between the Earth and Sun, allowing us to see them against the Sun’s disk. I reported on the 2012 transit of Venus,  which thanks to the likes of SLOOH, could be followed world-wide with ease.

SLOOH will also be covering the transit of Mercury (although you’ll have to sign-up to the service), while NASA will be providing a near-real-time feed of images event at nasa.gov/transit.

Credit: NASA

Credit: NASA

The transit will be visible from most parts of the Earth, commencing at around 11:00 GMT. Those with large enough telescopes or really good binoculars will be able to witness it for themselves, weather permitting, and providing they take the proper precautions to project the image of the sun onto a suitable surface. Never look at the Sun through an unfiltered optical instrument, even when it is low in the sky or heavily obscured by mist or fog – the concentration of infra-red and ultraviolet light is likely to severely damage your eyesight.

The transit will last some 7.5 hours, which offers plenty of time for people to tune-in to SLOOH or NASA to catch it. As well as offering us an opportunity to witness something which occurs around 13 times in a century, the transit presents scientists with a unique opportunity to study Mercury’s exosphere  – the tenuous atmosphere surrounding it and spreading tail-like behind it, away from the Sun.

To achieve this, the European-led Solar and Heliospheric Observatory (SOHO) will use two reactivated the Extreme ultraviolet Imaging Telescope and the Michelson Doppler Imager,two observe the transit. These instruments were shut down five years ago to conserve power aboard the craft, which orbits the Earth-Sun L1 lagrange point, 20 years into what had originally been a 3-year mission. At the same time, NASA’s Solar Dynamics Observatory (SDO), occupying a Geosynchronous orbit above the Earth will also observe the transit, thus providing two sets of data on the event which can be analysed and compared.

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