Tag: Spaceflight

Space Sunday: submarines, balloons and rockets

Posted on by Inara Pey
The four Galilean moons of Jupiter from volcanic Io (l) to distant Callisto (r). Europa and Ganymede (2nd and 3rd respectively) are thought to have liquid water oceans under their icy crusts, and each will be investigated by upcoming NASA (Europa) and European (Ganymede) missions. Callisto also may have a subsurface ocean, although it is thought to be more likely frozen or at least slushy ice. It will also be examined by the European mission

At the end of February / start of March 2017, NASA hosted the “Planetary Science Vision 2050 Workshop” at their headquarters in Washington, DC. The workshop covered a number of ideas for the future exploration of the solar system using automated means.

Two of the more interesting areas of discussion were the exploration of the “ocean worlds” of the solar system, notably Jupiter’s Europa and Saturn’s Enceladus. The other was options for exploring Saturn’s moon Titan.

The “Icy Worlds”

As I’ve recently reported Europa is already the target of the upcoming Europa Multi Flyby mission, due to launch in the early 2020, and which is now known once more by its earlier title of Europa Clipper. However, at the workshop, scientists looked at future options for exploring it,  starting with the lander mission already being planned as a follow-on mission.

What makes these icy worlds so interesting is that under their crusts of ice, there may well be oceans of liquid water. Europa and Enceladus in particular have demonstrated very strong signs that under a surface coating of ice, they have liquid water oceans, perhaps 100 km (62.5 mi) deep in the case of Europa.

Europa’s internal structure, showing the subsurface ocean which could be up to 100 km (62.5 mi) deep. This layer might also either be relatively solid ice or icy slush, depending on the amount of heat being generated deeper inside Europa

These oceans are kept in a liquid state due to gravitational flexing: they are constantly being pulled in different directions by the gravities of their parent planet and the other moons in orbit around it. The flexing generates heat, and this heat could be sufficient to keep the water trapped under the ice crust of such a world in a liquid state. It could also mean that the ocean bed of such a world might be the locations of hydrothermal vents and fumeroles which are pushing out the heat, energy, minerals and chemicals needed to kick-start life.

The reason Europa’s ocean might be liquid is flexing. The gravitational pull of Jupiter and from the other Galilean moons constantly plays on Europa, causing it to flex as it is pulled in different directions. This flexing generate heat deep inside the moon, and this heat could both radiate out to warm the waters of the ocean and give rise to hydrothermal vents of the sea bed, which could harbour basic life

Europa, Ganyemede and Callisto, around Jupiter show every indication of such sub-surface oceans, although Ganyemede’s and Callisto’s case, it might be more icy slush than liquid water. Both will be the subject of study by Europe’s Jupiter Icy Moons Explorer, due for launch in 2022.

Europa’s ocean is believed to be liquid both as a result of spectral analysis of the ice covering it, and because images of the moon captured by the Hubble Space Telescope appear to show huge geysers erupting from the moon’s south polar regions.

Geysers of water vapour have also been seen erupting from Enceladus by NASA’s Cassini mission, indicating it also has a liquid ocean under its covering of ice.

Worldlets like Ceres and Pluto also appear to have liquid interiors overlaying their cores, although the processes that might by allowing such liquid layers – likely water – have yet to be properly understood.

Of them all, Europa perhaps shows the strongest evidence for harbouring life-giving nutrients within its oceans, marking it as a prime candidate for study. This is because of the reddish-brown staining covering much of its surface. Most of this is likely debris from the huge volcanic eruptions which occur on Io, the innermost of the Galilean moons of Jupiter, and the one experiencing the greatest levels of gravitational flexing. However, some of Europa’s straining might be material deposited as a result of geyser action, particularly where the stains appear to run along many of the fault lines which crack Europa’s surface.

Given all this, planetary scientists are itching to get a vehicle onto the surface on Europa and – if possible, get one through the ice and into the ocean beneath it. Hence the discussions at the NASA workshop.

A dramatic line of plumes spray water ice and vapour from the south polar region of Saturn’s moon Enceladus as seen by the Cassini mission in February 2005. Similar venting of water may give rise to some of the brown stains of material covering much of Europa’s surface Credit: NASA/JPL / Space Science Institute

As I noted in writing about Europa Clipper (see the link above), a lander mission is already in the advanced planning stages thanks to strong support for missions to Europa in Congress. It could potentially take place just a couple of years after Europa Clipper arrives in orbit around Jupiter, and would have three mission objectives:

  • Search for biosignatures and signs of life by analysing the surface and subsurface deposits on Europa, particularly recently erupted material near the lander’s location
  • Analyse the composition of the surface ice and determine the proximity of liquid water beneath the ice
  • Attempt to identify the dynamic processes responsible for shaping Europa’s surface and its properties.
An artist’s impression of a possible Europa submersible, with it deployment system in the background. Credit: NASA

If the lander mission detects signs of life or strong evidence of life-giving materials within Europa’s ice sheet, then it will  likely pave the wave for the most ambitious mission of all: sending a vehicle to Europa with the means to penetrate the surface ice and release an automated submersible into the waters below to search for possible life.

While there is no time frame for such a mission, it has long been a goal for NASA and scientists. So much so that there have been numerous studies and even competitions for such vehicles, and a broad range of proposals and designs have been put forward. As such, it could be that such a mission could follow the Europa lander mission relatively quickly – perhaps within a decade.

Continue reading “Space Sunday: submarines, balloons and rockets” →

Space Sunday: Moon flights and the winds of Mars

Posted on by Inara Pey
The Dragon 2 crew capsule attached to its service module. Credit: SpaceX
The Dragon 2 crew capsule attached to its service module. Credit: SpaceX

While most private space tourism companies are busily going about various routes to offer sub-orbital flights to those who can afford them, Elon Musk’s SpaceX has stepped into the arena – and, as might be expected, made the bold announcement it will go one better: fly paying passengers around the Moon and back. And they plan to do it in 2018.

The announcement was made by Musk on Monday, February 27th during a press teleconference. If the flight goes ahead, it will allow two fare-paying passengers the opportunity to undertake a week-long journey out to and around the Moon, before returning to Earth. The flight would use a “free return” profile which would see it skim over the surface of the Moon and continue outward beyond it, possibly as far as 480,000 Km (300,000 mi) from the Earth (the average distance of the Moon from Earth is around 384,400km /  240,000 mi), before Lunar gravity takes over and hauls the vehicle back towards the Earth, where it would splash down.

It’s not clear how much the passengers would pay to be on the flight – but the going price for a seat aboard the Dragon 2 vehicle, which would be used for the flight, will be around US $58 million a pop to get to the International Space Station, once it enters service. It’s also far from clear if SpaceX can actually deliver on the goal of launching the flight in late 2018.

SapceX plan to use the Falcon Heavy as the launch vehicle for the lunar flight. When it enters service later in 2017, the Falcon Heavy will be the most powerful launch vehicle in the world today
SpaceX plan to use the Falcon Heavy as the launch vehicle for the lunar flight. When it enters service later in 2017, the Falcon Heavy will be the most powerful launch vehicle in the world

In order to take place, the flight first and foremost needs a launch vehicle and a suitable space vehicle. SpaceX plan to use their mighty Falcon Heavy and – as noted – their new Dragon 2 crewed vehicle. There’s just a couple of problems with both.

The Falcon Heavy is not due to fly until some time later in 2017, and even then it will not be rated for crewed launches. For that to happen, it will have to be certified for crew use, and depending on how the initial flights go, that could take time. In terms of the Dragon 2, that is not scheduled to enter service until 2018 – and even then, its primary function is to fly crews to and from  the International Space Station (ISS).

Ferry flights to the ISS are vastly different to going out around the Moon and back. To start with, the outward flight from Earth to the ISS can be measured in just a couple of days – around a quarter of the time needed for the lunar trip.  The velocity (delta vee)  imparted to a spacecraft going to the ISS (28,000 km/h / 17,500 mph) is also a lot less than required to go to the Moon (40,000 km/h / 25,000 mph).

Elon Musk unveils a mock-up of the Dragon V2 capsule in May 2014. SpaceX now has their firs NASA contract to fly a crew to the ISS aboard the vehicle, probably in 2018
Elon Musk unveils a mock-up of the Dragon 2 capsule in May 2014.Credit: SpaceX

This means a returning Dragon 2 will be re-entering the Earth atmosphere a lot faster than the same craft coming back from the ISS, and will have to face much higher re-entry temperatures and a harsher deceleration regime. While the Dragon 2 can in theory do so, it is likely that significant testing on uncrewed vehicles will be required before the Federal Aviation Authority and NASA agree to any such flight taking place. On top of this, it will have to be demonstrated that the Dragon 2 can be outfitted for a deep space mission and keep a crew alive and well for around 7-8 days.

Given all this, there are widespread doubts the company can meet a 2018 deadline for such a mission – and SpaceX has tended to be ambitious with its time frames for achieve goals. They had originally slated 2013 as the year in which the Falcon Heavy would make its first flight – although in fairness, setbacks following the loss of two Falcon 9 vehicles also contributed to its launch being pushed back to 2017.

Red Dragon Delayed

As further evidence of SpaceX presenting time frames which are perhaps a little ambitious, on February 17th, the company announced its mission to land a variant of the Dragon 2 – dubbed Red Dragon – on Mars has been pushed back from 218 to 2020.

The aim of the mission so to fly an uncrewed 10-tonne Dragon 2 vehicle to Mars and land it safely. In doing so, the company hopes to gain valuable data on landing exceptionally heavy vehicles on Mars using purely propulsive means. This is because crewed landing vehicles on a Mars mission are liable to have a mass of at least 40 tonnes – far too much to be safely slowed in a descent through the thin Martian atmosphere by parachutes.

A SpaceX / NASA infographic outlining the Red Dragon mission - now slated for 2020
A SpaceX / NASA infographic outlining the Red Dragon mission – now slated for 2020

The planned mission would be undertaken entirely at the company’s own expense, although it would can science instruments and experiments supplied by NASA. For Musk it, and possibly three further Red Dragon mission which could follow it in the 2020-2024 time frame, is a vital precursor to greater ambitions for Mars.

As he outlined in September 2016 (see: Musk on Mars), Musk plans to start launching crewed missions to Mars, possibly before 2030. The initial missions will doubtless be modest in size in terms of crew and goals. However, his overall stated goal is to kick-start the colonisation of Mars. To do that, he plans to use vehicles massing at least 100 tonnes and which can make a propulsive landing on Mars. Whether he can succeed in even the step to land a crew on Mars  – and bring them back to Earth – remains to be seen. However, his Red Dragon mission is an important first step.

Continue reading “Space Sunday: Moon flights and the winds of Mars” →

Space Sunday: TRAPPIST-1, planet 9 and Europa

Posted on by Inara Pey
An artist's impression of the seven TRAPPIST planets, with -1b lower left and -1h lower right. The three planets in the star's habitable zone, -!e, -1f and -1g are the right-hand three in the top row. Credit: NASA
An artist’s impression of the seven TRAPPIST planets, with -1b lower left and -1h lower right. The three planets in the star’s habitable zone, -!e, -1f and -1g are the right-hand three in the top row. Credit: NASA

I recently wrote a space update special on the TRAPPIST-1 star system with its seven roughly Earth-sized planets. Since then, there has been speculation about whether any of them might support life, and what conditions for life might be like.

Whether life may have arisen on any of the worlds is tough question to answer. Three of the seven lie within the “habitable zone” where liquid water might exist (TRAPPIST-1e, -1f and -1g) – which is a positive for life as we know it. But for that liquid water to remain liquid, the planets must have an atmosphere. Currently, only TRAPPIST-1b and -1c have, through spectral analysis, been shown to harbour atmospheres, but these seem to be limited in scope, and could range from a water vapour rich atmosphere through to an environment similar to that of Venus.

On the negative side of the equation, the nature of their parent star, a super cool red dwarf with all internal action entirely convective in nature, means that all seven planets are likely subject to sufficient irradiation in the X-ray and extreme ultraviolet wavelengths to significantly alter their atmospheres, potentially rendering them unsuitable for life. Further, all seven are tidally locked, meaning they always keep the same face towards their parent star. This will inevitably give rise to extreme conditions, with one side of each world bathed in perpetual daylight and the other in perpetual, freezing darkness, resulting in extreme atmospheric movements and likely harsh weather.

Comparing the TRAPPIST-1 system with the solar system. Credit: European Southern Observatory / O. Furtak
Comparing the TRAPPIST-1 system with the solar system. Credit: European Southern Observatory / O. Furtak

Daylight on the planets would also be very different. Although one side of these worlds be forever in daytime, and despite the relative proximity with which they orbit their parent star, days on their surfaces would never be much brighter than sunset here on Earth, both in terms of colour and light intensity. This is because most of the light emitted by TRAPPIST-1 is radiated in the infra-red wavelengths, rather than visible wavelengths.

One the more positive side of the equation, despite the low levels of visible light, TRAPPIST-1 could still be able to sufficiently warm an atmospheres the planets might have, and the weather conditions might actually dissipate this warmth evenly over the planet’s surface, perhaps making it more hospitable to life.

It’s also likely the planets experience a lot of tidal flexing as they come under the influence of one another as well as their parent star. This flexing might give rise to hydrothermal and volcanic vents, which in turn could provide the necessary heat (energy), minerals and chemicals necessary to kick-start basic life.

Artist's impression of the three planets in TRAPPIST-1's habitable zone and to scale relative to one another. -1e (l) is the most likely to have extensive liquid water. It is 92% as big as Earth, with a mass of 62% that of Earth. It orbits its parent star about 10.8 times the distance from Earth to the Moon. -1f (c) is 1.04 times the size of Earth, but with only 62% of its mass. It is potentially water rich, and gets as much light from its star as Mars does from the Sun. -1g (r) is the outermost of the three
Artist’s impression of the three planets in TRAPPIST-1’s habitable zone and to scale relative to one another. -1e (l) is the most likely to have extensive liquid water. It is 92% as big as Earth, with a mass of 62% that of Earth. It orbits its parent star about 10.8 times the distance from Earth to the Moon. -1f (c) is 1.04 times the size of Earth, but also with  62% of its mass. It is potentially water rich, and gets as much light from its star as Mars does from the Sun. -1g (r) is the outermost of the three. It is 1.13 times Earth’s size with 1.34 times its mass. It is far enough away from its parent star that the surface is likely to be entirely frozen, but the gravitational influence of the other planets could give rise to a liquid water ocean under the ice. Credit: NASA

Studies of the TRAPPIST system will continue using the Spitzer and Hubble space telescopes and via ground-based observatories. However, as mentioned in my special report, it is likely to be the James Webb Space Telescope which will hopefully reveal many of the secrets of the TRAPPIST-1 system.

That said, and for those still wondering about intelligent life arising on any of these worlds, SETI, the Search for Extra-Terrestrial Intelligence has been “listening in” on the star for indications of radio traffic for some time (pre-dating the discovery of the first two planets in the system in 2016). Those surveys haven’t revealed any kind of radio emissions from the system that might be of artificial origin, but now we know there are seven planets, SETI has marked TRAPPIST-1 for further investigations with their Allen Telescope Array (ATA).

A Further Clue in the Hunt for Planet 9

Last year, Caltech astronomers Mike Brown and Konstantin Batygin found indirect evidence for the existence of a large planet in the outer reaches of our Solar System well beyond Pluto; since then, the search has been on. I first covered the hunt in January 2016, and followed it with updates in February 2016 and October 2016, and it now seems a new clue to the planet’s existence may have been revealed.

Planet X, if it exists,could equal Neptune in size, and orbits the Sun 200 times further away than Earth. Credit: Caltech / R. Hurt
Planet X, if it exists,could equal Neptune in size, and orbits the Sun 200 times further away than Earth. Credit: Caltech / R. Hurt

Astronomers using the Gran Telescopio CANARIAS (GTC) in the Canary Islands looked at two distant asteroids, called Extreme Trans Neptunian Objects (ETNOs). Spectroscopic observations 2004 VN112 and 2013 RF98 suggest that the two were once a binary asteroid pairing that were pulled apart as a result of the influence of a mass massive body between 10 and 20 Earth masses in size and about 300 to 600 AU from the Sun. As a result of this, the two bodies drew further and further apart over, time they became more and more separated to become how we see them today.

“The similar spectral gradients observed for the pair 2004 VN112 – 2013 RF98 suggests a common physical origin,” said Julia de León, an astrophysicist at the Instituto de Astrofísica de Canarias (IAC). “We are proposing the possibility that they were previously a binary asteroid which became unbound during an encounter with a more massive object.”

de León and his team carried out thousands of computer-based simulations to see how this might have happened, and found the most consistent result suggested the bodies were separated as a result of a close passage by a massive planetary object around 5-10 million years ago.

As it might be: estimates concerning Planet Nine's possible size, mass, etc., should it exist. Credit: Space.com / Karl Tate
As it might be: estimates concerning Planet Nine’s possible size, mass, etc., should it exist. Credit: Space.com / Karl Tate

What is particularly interesting here is that the location of the two asteroids, coupled with the suggested mass of the body which pulled them apart and the distance it is believed to have been from the Sun, also fit the broader parameters for where the orbit of Planet 9 might reside, and the estimated mass of the planet. Thus, when combined with the eccentric orbits of several Kuiper Belt Objects believed to have been perturbed in their orbits around the Sun by planet 9, it gives further credence to the idea it really is out there, somewhere.

When – and if – it might eventually be found is open to question. However, it is hoped that a  recently started “citizen scientist project will encourage amateur astronomers around the world to join in the hunt for Planet 9.

Continue reading “Space Sunday: TRAPPIST-1, planet 9 and Europa” →

Space Sunday: Jupiter, Enceladus and Ceres; SLS, SpaceX and Dream Chaser

Posted on by Inara Pey
This stunning enhanced colour images of Jupiter's south polar region was captured by the JunoCam instrument aboard the Juno spacecraft on February 2nd, 2017. It reveals a complex series of interactions occurring in the fast-spinning atmosphere
This stunning enhanced colour images of Jupiter’s south polar region was captured by the JunoCam instrument aboard the Juno spacecraft on February 2nd, 2017. It reveals a complex series of interactions occurring in the fast-spinning atmosphere. Credit: NASA/JPL / SwRI

Following its latest close flyby of Jupiter – passing just 4,200 km (2,600 mi) above the gas giant’s cloud tops on February 2nd, 2017, NASA’s Juno mission spacecraft is now heading away from the planet once more and the next of its 53.5 day orbits. As I’ve previously reported in these Space Sunday columns, the original plan had been to use one of these close passes over the planet (October 2016), in conjunction with a sustained burn of the spacecraft’s British-built rocket motor, to move it into a short, 14-day period orbit around Jupiter.

However, a potential fault detected within the engine system meant the October burn was cancelled, and since then, engineers had been trying to assess if the issue  – a set of faulty valves – could be overcome, and the consequences of attempting an additional engine burn if not. No definitive answer has been found and so, following the February 2nd flyby, the decision was taken to cancel all plans for the engine burn and leave the spacecraft in its current 53.5 day orbit around Jupiter.

Doing so doesn’t compromise the overall mission objectives, but it does reduce the number of close passes over Jupiter the vehicle can make. If the reduced orbital period had been possible, the spacecraft would have made some 30 close flybys over Jupiter’s cloud tops during the primary mission period, set to end in July 2018. Remaining in the 53.5 day orbit means it will only make around 12 such close flybys in the same period.

The Juno spacecraft was supposed to complete two 53-day orbits around Jupiter, then lower its orbit Oct. 19 to fly around the planet once every 14 days. That engine burn has been postponed. Credit: NASA / JPL
The Juno spacecraft was supposed to complete two 53.5-day orbits around Jupiter in July and August 2016 (shown in green), before using its main engine to brake itself into a 14-primary science orbit (shown in blue). Due to continued concerns about the vehicle’s engine unit, the decisions has now been made to leave it in the 53.5 day orbit. Credit: NASA / JPL

A positive point with the spacecraft remaining in its more extended orbit is that it will spend less time within the harsher regions of Jupiter’s radiation belts, and could thus remain active for longer than the primary mission period – and mission planners are already considering applying for further funding to allow the mission to extend beyond July 2018. It also means that the spacecraft will be able to engage in additional science activities.

The close encounters with Jupiter have already allowed the spacecraft to probe deep within the planet’s cloud belts and discover they extend far deeper into the planet’s atmosphere than had been imagined, and that Jupiter’s magnetic field and auroras are more powerful than previously thought.

“Juno is providing spectacular results, and we are rewriting our ideas of how giant planets work,” Juno principal investigator Scott Bolton, of the South-west Research Institute in San Antonio, Texas, said of the decision to leave the spacecraft in its current orbit. “The science will be just as spectacular as with our original plan.”

NASA Considering Crewed Option for Orion / SLS First Launch

NASA is considering making the first launch of its new Space Launch System (SLS) rocket, currently slated for September 2018, a crewed mission.

Under the agency’s existing plans, the first launch of the new rocket, topped by an Orion Multi-Purpose Crew Vehicle and dubbed Exploration Mission 1 (EM-1), would have seen SLS send an uncrewed Orion vehicle to the Moon and back, with around 6 days spent in lunar orbit. A crewed flight of the SLS / Orion combination would not take place until at least 2021, when crew would use Orion to rendezvous to a small asteroid previously captured via robotic means and moved to an extended orbit around the Moon – an idea which has garnered a certain amount of criticism from politicians.

An artist's impression of a Space Launch System / Orion combination lifting off from Kennedy Space Centre's Pad 39B. Credit: NASA
An artist’s impression of a Space Launch System / Orion combination lifting off from Kennedy Space Centre’s Pad 39B. Credit: NASA

If approved, the new proposal – put forward by NASA’s Acting Administrator, Robert Lightfoot – would see the planned EM-1 mission pushed back to 2019 (allowing the Orion vehicle to be outfitted with the crew lift support and flight systems) and flown with a crew of two. While this would mean a delay in the initial launch of SLS / Orion, it could ultimately accelerate NASA’s plans, allowing the agency to present a wider choice of crewed missions in the 2020s, and respond to criticism that it is not doing enough to demonstrate how it plans to achieve a return to the Moon and / or  missions to Mars.

Enceladus: Cradle for Life?

On February 17th, 2005 NASA’s Cassini space probe, part of the Cassini / Huygens mission, made its first flyby of Saturn’s moon Enceladus.

Scientists were naturally curious about the 500 km (360 mi) diameter moon, which is the most reflective object in the solar system, but assumed it was essentially a dead, airless world. However, Cassini immediately found this was not the case.

A dramatic plume sprays water ice and vapor from the south polar region of Saturn's moon Enceladus. Cassini's first hint of this plume came during the spacecraft's first close flyby of the icy moon on February 17, 2005. Credit: NASA/JPL / Space Science Institute
A dramatic plume sprays water ice and vapour from the south polar region of Saturn’s moon Enceladus. Cassini’s first hint of this plume came during the spacecraft’s first close flyby of the icy moon on February 17, 2005. Credit: NASA/JPL / Space Science Institute

The first thing that happened was the magnetometer on the spacecraft revealed that Saturn’s magnetic field, which envelops Enceladus, was perturbed above the moon’s south pole in a way that didn’t make sense for an inactive world – it was as if there was some interaction with an atmosphere.

In the second flyby, a month later, Cassini found the interaction seemed to suggest a plume of water vapour was rising from the moon. Then, in the third flyby, in July 2005, the probe imaged geysers of water vapour erupting from the moon’s south polar region, and thus Enceladus became the target of intense study. So much so, that while only those initial 3 flybys of the moon had been a part of the primary Cassini /Huygens mission profile, the mission was updated to allow 20 more flyby of the moon.

Today, we know that beneath the mantle of ice enclosing Enceladus there is an ocean of liquid water – the geysers are the results of that water breaking through this ice and jetting into space, giving rise to Saturn’s E-ring in the process. This ocean is likely to be warmed and kept liquid by hydrothermal vents on the sea floor, and these in turn – just like the vents theorised to be on the ocean floor of Jupiter’s Europa – might provide all the ingredients for basic life to arise.

To celebrate the 12th anniversary of Cassini’s discoveries with Enceladus, NASA has released a video documenting those initial findings from 2005.

Continue reading “Space Sunday: Jupiter, Enceladus and Ceres; SLS, SpaceX and Dream Chaser” →

Space Sunday: Martian quandaries, universal epochs and Jovian journeys

Posted on by Inara Pey
"Yellowknife Bay" a region examined by the Curiosity Rover in 2012/13 indicated that a lake was once present in Gale Crater. However, the same rock has revealed that potentially, there was not sufficient carbon dioxide present in the atmosphere to help keep the water unfrozen
“Yellowknife Bay” a region examined by the Curiosity Rover in 2013 indicated that a lake was once present in Gale Crater. However, the same rock has revealed that potentially, there was not sufficient carbon dioxide present in the atmosphere to help keep the water unfrozen. Credit: NASA

Mars scientists are wrestling with a problem. Ample evidence says ancient Mars was sometimes wet, with water flowing and pooling on the planet’s surface. Yet, the ancient sun was about one-third less warm and climate modellers struggle to produce scenarios that get the surface of Mars warm enough for keeping water unfrozen.

A leading theory is that ancient Mars had a thicker carbon-dioxide atmosphere forming a greenhouse-gas blanket, helping to warm the surface. However an analysis of data from NASA’s Mars rover Curiosity, suggests that even 3.5 billion years ago there was too little carbon dioxide present in the Martian atmosphere to provide enough greenhouse-effect warming to prevent water freezing.

The source of these findings is the very same bedrock in which the rover found sediments from an ancient lake in which microbes might have thrived. When analysing the bedrock, Curiosity detected no carbonate minerals, leading to the conclusion that Mars’ atmosphere was almost devoid of carbon dioxide when the lake existed 3.5 billion years ago. And that’s a quandary for scientists.

Curiosity took this selfie while at "Yellowknife Bay" in 2013 whilst gathering rock samples for analysis. Note that while the shadow of the rover's robot arm can be assn, the arm itself is blanked from the images purely as a result of the angles used in individual shots and the way the images have been stitched together to provide a view of the rover
Curiosity took this selfie while at “Yellowknife Bay” in 2013 whilst gathering rock samples for analysis. Note that while the shadow of the rover’s robot arm can be seen, the arm itself is blanked from the images purely as a result of the angles used in individual shots and the way the images have been stitched together to provide a view of the rover. Credit: NASA

“We’ve been particularly struck with the absence of carbonate minerals in sedimentary rock the rover has examined,” Thomas Bristow, the principal investigator for Curiosity’s Chemistry and Mineralogy (CheMin) instrument,  the primary source of the analysis work. “It would be really hard to get liquid water even if there were a hundred times more carbon dioxide in the atmosphere than what the mineral evidence in the rock tells us.”

In water, carbon dioxide combines with positively charged ions such as magnesium and ferrous iron to form carbonate minerals, and CheMin can identify carbonate if it makes up just a few percent of the rock. Yet Curiosity has made no definitive detection of carbonates in any lakebed rocks sampled since it landed in Gale Crater in 2012. However, other minerals – magnetite and clay minerals – not only indicated in the same rocks indicate the ions needed to form carbonates were readily available, they also provide evidence that subsequent conditions never became so acidic that carbonates would have dissolved away over time.

The dilemma between a warm, wet Mars and the lack of carbonates has actually been growing for years. For two decades researchers have been using spectrometers on Mars orbiters to search for carbonate that could have resulted from an early era of more abundant carbon dioxide in the atmosphere, only to find far less than anticipated. Yet clues such as isotope ratios in today’s Martian atmosphere continue to indicate the planet once held a much denser atmosphere than it does now, which has largely been seen as being rich in carbon dioxide. Thus, a paradox has arisen.

Curiosity uses a spectrometer on its robot arm to check a rock dubbed "John Klein" in "Yellowknife Bay" for its suitability as a drilling target, January 25th, 2013. The drill itself can be seen on the robot arm's "hand", pointing up and to the right
Curiosity uses a spectrometer on its robot arm to check a rock dubbed “John Klein” in “Yellowknife Bay” for its suitability as a drilling target, January 25th, 2013. The drill itself can be seen on the robot arm’s rotating “hand”, pointing up and to the right. Credit: NASA

It had been thought that the lack of evidence for carbonates when seen from orbit could simply be the result of  dust covering them, or the carbonates having moved underground. Finding them would thus resolve the paradox and reveal what had happened. However, the Curiosity results tend to overturn this idea. Simply put, the rover has failed to detect carbonate minerals precisely where they should be located, within rocks formed from sediments deposited under water.

“This analysis fits with many theoretical studies that the surface of Mars, even that long ago, was not warm enough for water to be liquid,” said Robert Haberle, a Mars-climate scientist at NASA Ames. “It’s really a puzzle to me.”

One idea put forward is that perhaps the lake was never a body of open water, but was covered in ice. The problem with this idea is none of the expected evidence for an ice-covered lake, such as large and deep cracks called ice wedges, or “dropstones,” which become embedded in soft lakebed sediments when they penetrate thinning ice, have been found. Thus, scientists have a lot of head scratching and theorising to do in order to make sense of the dilemma.

Traversing Mars with Curiosity

A simulated Curiosity rolls over the "Naukluft Plateau" in this still from Seán Doran's video simulation of the rover's traverse
A simulated Curiosity rolls over the “Naukluft Plateau” in this still from Seán Doran’s video simulation of the rover’s traverse. Credit: Seán Doran

Ever wondered what it would be like to witness Curiosity trundling across the surface of Mars? Seán Doran has. What’s more, he’s been putting together animated films using Digital Terrain Model (DTM) data from the HiRISE imaging system on NASA’s Mars Reconnaissance Orbiter together with photomosaics of images from the rover, and combining them with a drivable correctly scaled model of the rover to provide movies of Curiosity as it rolls across Mars.

Continue reading “Space Sunday: Martian quandaries, universal epochs and Jovian journeys” →

Space Sunday: Juno and Jupiter, China, Google and the Moon

Posted on by Inara Pey
An artist's impression of Juno firing its main engine at it passes over Jupiter's cloud tops. Credit: NASA
An artist’s impression of Juno firing its main engine at it passes over Jupiter’s cloud tops. Credit: NASA

On Thursday, February 1st, 2017, NASA’s Juno spacecraft completed its fourth 53.5 day orbit of Jupiter since its arrival on July 4th, 2016. The vehicle, reached perijove – the point at which it is closest to Jupiter’s cloud tops at 12:57 GMT (07:57  EST), just 4,300 km (2,670 mi) above the cloud top at a velocity of about 208,000 km/h (129,300 mph) relative to the planet.

As there were no plans to utilise the craft’s main engine to slow the craft into a 14-day orbit around Jupiter – a issue with a potentially faulty set of valves in the motor system is still being investigated – the spacecraft was able to conduct a “close-up” data gathering exercise as it swept around Jupiter, gathering data on atmospheric radiation and plasma.

Also active during the flyover was the spacecraft’s imaging system, dubbed “JunoCam”. This has already captured some stunning images of Jupiter during past perijoves, and the hope is it will have done so again. Thanks to an outreach programme in which NASA invite “citizen scientists” to download raw JunoCam images and process them at their leisure, together with a programme that allows the public to suggest areas the camera might image during each perijove, JunoCam has become extremely popular.

A stunning view of the intricate boundaries between Jupiter's bands of cloud, as captured by JunoCam during the December close pass over the cloud tops in December. The white spot is one of the
A stunning view of the intricate boundaries between Jupiter’s bands of cloud, as captured by JunoCam during the December close pass over the cloud tops in December. The white spot is one of the “pearls” – thought to be a storm – which form bright “strings” in Jupiter’s southern hemisphere

The next close flyby will be on March 27th. It’s not clear yet whether this will be a science pass, or whether the Juno Mission team will risk firing the vehicle’s motor to slow it into the planned 14-day orbit. If they do, then the science suite will likely be powered down to conserve electrical power during the manoeuvre.

But even if Juno doesn’t achieve that final 14-day orbit, its science mission will not be unduly compromised. The craft will be able to meet all of its mission goals even if it remains in the 53.5-day polar orbit it currently occupies.

A major reason for Juno's polar orbit around Jupiter is that it allows the vehicle to pass
A major reason for Juno’s polar orbit around Jupiter is that it allows the vehicle to pass “between” the most powerful and intense radiation belts emanating from the planet. However, as the mission continues, the tilt of the spacecraft’s orbit relative to the planet means that over time, it will increasingly delve into these more intense radiation belts. Credit: NASA

The Jovian system is a place of intrigue. Not only is Jupiter a potential key to helping us understand the evolution of such gas giant planets, it sits at the centre of a gigantic magnetosphere so vast and powerful, it extends 5 million kilometres (3 million miles) towards the Sun, and reaches out as far as the orbit of Saturn – 651 million kilometres (407 million miles) – in the other direction.

All of Jupiter’s Galilean moons,  Callisto, Ganymede, Europa and Io, orbit within this magnetosphere, “bubble” and are affected by it. However, it is innermost Io which has the greatest interaction, and a proposal has been put forward to have Juno examine the relationship between Io and Jupiter in greater detail.

A false colour enhanced image of a volcanic plume above Io. Credit: NASA
A false colour enhanced image of a volcanic plume above Io. Credit: NASA

With Jupiter on one side, and the other three big moons on the other, Io, roughly 320 km (200 mi) small in diameter than the Moon, is constantly being flexed by the opposing gravitational forces. This flexing physically manifests in the moon being the most volcanically active place in the solar system. At any given time, Io has an estimated 300 active volcanoes belching sulphur, sulphur dioxide gas and fragments of basaltic rock up into the space above itself to interact  with Jupiter’s magnetosphere.

As the material from the eruptions rise from Io, it is bombarded by high-energy electrons withing Jupiter’s magnetsphere.  These ionise the ejected material, forming a vast plasma torus of highly energised (aka radioactive) particles around the Jupiter and straddling Io’s orbit. In addition, Jupiter’s magnetic field also couples Io’s polar atmosphere to the planet’s polar regions, pumping this ionised material through two “pipelines” to the magnetic poles and generating a powerful electric current known as the Io flux tube, which can most visibly be seen (if you are close enough) as Jupiter’s polar aurora.

Continue reading “Space Sunday: Juno and Jupiter, China, Google and the Moon” →