Tag Archives: Astronomy

Space Sunday: Flying over Mars, JUICE for Jupiter and black holes

An impact crater which formed between July 2010 and May 2012 and imaged by the HiRISE camera on the Mars Reconnaissance Orbiter, is one of the locations featured in “A Fictive Flight Above Real Mars” by Jan Fröjdman. Credit: Jan Fröjdman; original anaglyph image NASA/JPL / University of Arizona

Ever wondered what it would be like to actually fly over Mars? I have – although I admit, I’m utterly entranced by that red world and the potentials it presents. Finnish film-maker Jan Fröjdman has as well – only he’s taken the idea a step further and produced a remarkable video,  A Fictive Flight Above Real Mars. Last just over 4.5 minutes, the film takes us on a flight over some of the must remarkable scenery imaginable, using high-resolution images and data returned by NASA’s Mars Reconnaissance Orbiter (MRO).

It’s a stunning piece showing many of the more intriguing features of Mars: the recent impact crater see in the still at the top of this article; the ice walls and melt holes of the Martian poles; gullies and cliffs rutted and marked by RSLs – recurring slope lineae – which might or might not be the result of liquid activity; the ripples of sand dunes, and the winding forms of channels which might have been shaped by the passage of water.

To make the film, Fröjdman used 3-D anaglyph images from HiRISE (the High Resolution Science Imaging Experiment aboard MRO), which contain information about the topography of Mars surface. The work involved manually picking more than 33,000 reference points in the anaglyph images, and then processing the results through six pieces of software to achieve a sense of motion and panning across the surface of Mars.

In putting the film together, Fröjdman  wanted to create a real feeling of flying over Mars and of recapturing the feel of video footage shot by the Apollo astronauts as they orbited the Moon. To help with the latter, he overlaid the video with image cross-hairs of the kind seen in some of the Apollo footage, and added little bursts of thruster firings to simulate a vehicle manoeuvring in the thin atmosphere. The film concludes with a main engine firing, presumably to lift the vehicle back into orbit.

NASA and SpaceX Consider Red Dragon Landing Site

And staying with Mars: NASA and SpaceX have started the process of selecting a landing site for SpaceX’s planned Red Dragon mission to Mars in 2020. The ambitious mission will see the company attempt to land a 10-tonne Red Dragon capsule on Mars purely by propulsive means. While paid for entirely by the company, the mission will feature a science suite provided by NASA.

There are two major criteria governing any landing site location: scientific interest, and the potential for colonisation – the 2020 mission being the first of a number which SpaceX plans to uses as precursors for human missions to Mars. As such, it had initially been decided that any landing sites put forward must be near the equator, for solar power; near large quantities of ice, for water and at low elevation, for better thermal conditions.

NASA initially identified four potential locations on Mars’ northern hemisphere which meet the broad criteria for the mission – but examination of three of them using the HiRISE system on the Mars Reconnaissance Orbiter showed they are rocky enough to pose a threat to landing a vehicle the size and mass of Red Dragon. This currently leaves a short-list of one, in the shape of Arcadia Planitia, a smooth plain containing fresh lava flows and which has a large region that was shaped by periglacial processes which suggest that ice is present just beneath the surface.

Acadia Planitia is the current sole contender to be the landing site for the SpaceX Mars 2020 mission

However, negating this is the plain’s relatively high northern latitude (40-60 degrees north), which would reduce the amount of sunlight a base of operations there would receive in the winter months. While Amazonis Planitia to the south offers a similar youthful surface, much of which is relatively smooth, it is largely volcanic in origin and unlikely to harbour sub-surface water ice which can be easily accessed.

Given both of these point, it is likely other possible landing sites will be proposed in the coming months.

Curiosity Reveals More Wheel Damage

It’s been a while since my last report on NASA’s Mars Science Laboratory rover, Curiosity. This is mostly being the updates coming out of JPL have slowed mightily in recent months.

At present, Curiosity is examining sand dunes on the lower slopes of “Mount Sharp”. Once finished, it will proceed up higher to a feature known as “Vera Rubin Ridge”, inspecting a layer that is rich in the mineral hematite. From there, it will proceeded to even higher elevations to inspect layers that contain clays and sulphates. This will require a drive of some 6 km (3.7 mi) uphill, and so will require time to complete.

A recurring area of concern for the mission – albeit not serious at this point – is the wear and tear on the rover’s wheels. In 2013, Curiosity suffered greater than expected damage to its six wheels while traversing some exceptionally rough terrain.  Although the damage was nowhere near severe enough to impeded the rover’s driving abilities, it did result in engineers keeping a much closer eye on the condition of Curiosity’s wheels using the imaging system mounted on the rover’s robot arm.

The latest of these checks was performed on  Sunday, March 19th, 2017, and it revealed two small breaks in the raised treads (“grousers”) on the rover’s left middle wheel. These seem to have occurred since the last wheel check at the end of January, 2017. These treads perform two major tasks: bearing the brunt of the rover’s weight and providing most of the traction for a wheel.

The broken “grousers” (“treads”) on one of Curiosity’s six wheels, together with older puncture holes through the wheel, as imaged on March 19th, 2017. Credit: NASA/JPL

Following the 2013 damage, testing on Earth suggested that significant breaks in three “grousers” on a wheel would indicate it has passed 60% of its expected lifespan. However, the mission team emphasise the rover has already driven more than 60% of the total distance needed for it to make it to all of its scientific destinations. As such, while the breaks will be monitored, they are not a cause for immediate or grave concern.

Overall, confidence remains high that Curiosity will achieve all of its expected science goals and will likely make an extended traverse up the side of “Mount Sharp”.

A rover’s progress: the 16 km (10 mi) travelled by Curiosity so far, and potential for future explorations up the side of Aeolis Mons. Credit: NASA/JPL / T. Reyes

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Space Sunday: 100+ planets, taking a balloon to orbit, and budgets

A chart showing the to-scale sizes of two planets, 19 moons, 2 asteroids, and 87 trans-Neptunian objects, all of which could technically be considered planets orbiting our Sun. Credit: Emily Lakdawalla. Data from NASA / JPL, JHUAPL/SwRI, SSI, and UCLA / MPS / DLR / IDA, processed by Gordan Ugarkovic, Ted Stryk, Bjorn Jonsson, Roman Tkachenko, and Emily Lakdawalla

When is a planet not a planet – or more precisely, when should what is not regarded as a planet be a planet?

Right now, according to the International Astronomical Union (IAU), our solar system comprises eight formally recognised planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. That’s been the case since 2006, when the IAU opted to classify bodies orbiting the Sun in three ways:

  • As planets – defined as a) celestial bodies that (a) are in orbit around the sun; b) have  sufficient mass for their self-gravity to overcome rigid body forces so they assume a hydrostatic equilibrium (nearly round) shape; c) have cleared the neighbourhood around their orbit of other objects
  • As Dwarf planets – defined as celestial bodies which a) orbit the sun; b) have sufficient mass for their self-gravity to overcome rigid body forces to assume hydrostatic equilibrium (aka “is nearly round” in shape);  c) have not cleared the neighbourhood around their orbit; and d) is not a natural satellite
  • As Small Solar System bodies:  all other objects except satellites orbiting the Sun.

A composite image showing Pluto and Charon to scale to one another (but not at a scale separate from one another) using images returned by the New Horizons mission. Credit: NASA / John Hopkins University APL / SwRI

Thus, since 2006, Pluto has been a dwarf planet. However, moves are afoot to get things changed – and not just for Pluto.

In a paper authored by planetary scientists involved in the New Horizons mission which zipped through the Pluto system in July 2015, there is a call for the term “planet” to be redefined; if not by the IAU then at least in popular use. Should it happen, it could see the number of planets in the solar system leap from 8 to over 100.

The scientists argue that the IAU definition of “planet” focuses only on the intrinsic qualities of the body itself, rather than external factors such as its orbit or other objects around it. In fact, under the IAU’s definition, Earth, Mars, Jupiter and Neptune don’t actually qualify as “planets” as none meet the third criteria (c) – Earth, for example, has regular “close encounters” with asteroids which cross its orbit. Instead, the team offer a simpler definition:

A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has enough gravitation to be round due to hydrostatic equilibrium regardless of its orbital parameters.

Such a definition would mean that Pluto could regain its planetary status – as would the proto-planet (or small solar system body) Ceres, the dwarf planets of 136199 Eris (discovered in 2005, and the trigger-point for Pluto’s “downgrading”) , 136472 Makemake, and 136108 Haumea, together with (possibly) 50000 Quaoar, 90377 Sedna, 90482 Orcus and a host of trans-Neptunian objects tumbling around the Sun. Nor is that all; the new definition would also mean that the likes of  Jupiter’s Galilean moons, Saturn’s Titan and  Enceladus, Neptune’s Triton and many other bodies we regard as “moons” would be lifted to planetary status – including our own Moon.

A composite image using data gathered by the radar imager aboard NASA’s Cassini mission to Saturn to look through the normally opaque haze of Titan’s dense atmosphere to reveal its planet-like surface. Credit: NASA/JPL / University of Arizona

The paper proposing the change will be presented at the Lunar and Planetary Science Conference on March 20th to 24th, 2017 in Texas. And it has already come in for some criticism.

Mike Brown is the scientist largely behind Pluto’s demotion. Currently engaged in the search for the elusive “Planet Nine”, he (somewhat harshly) sees the efforts of the New Horizons team to get Pluto reclassified as being  about them wanting the prestige of having run a planetary mission, more than anything else.

However, there are valid reasons for seeking some kind of change, even if it is only informal. One is as basic as gaining more public interest in efforts to explore and understand the many environments found on planets and moons alike within our solar system.

“Every time I talk about this [the science and data gathered about Pluto by New Horizons] to the general public, the very next thing people say is ‘Pluto is not a planet any more’,” said Kirby Runyon, the lead author of the paper. “People’s interest in a body and exploring it seems tied to whether or not it has the name ‘planet’ labelled on it.”

How Pluto compares with other large Trans-Neptunian Objects, some of which also have their own moons. Earth and our moon can be seen at the bottom of the picture. Credit: Lexicon / Wikipedia, using NASA / Hubble Space Telescope data

There are scientific reasons for the definition to be broadened as well. Places like Pluto, Ceres, Europa, Io, Ganyemede, Callisto and Triton all evidence geophysical, hydrothermal, atmospheric and other characteristics very much in keeping with bodies such as Earth, Mars, and Venus. They are thus of exceptional interest to planetary scientists the world over. In fact, many of them (like Pluto) are completely re-writing our understanding of “planetary bodies”.

Ultimately, the team behind the paper aren’t going to put their proposal before the IAU for a change in the “official” definition of “planet”.  “As a geophysical definition, this does not fall under the domain of the IAU, Runyon notes, “[It]  is an alternate and parallel definition that can be used by different scientists. It is “official” without IAU approval, partly via usage.”

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Space Sunday: TRAPPIST-1, planet 9 and Europa

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.

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Space update special: the 7-exoplanet system

An artist's impression of the sky from the outermost of the three TRAPPIST exoplanets in the star's habitable zone (see the 360-video below)

An artist’s impression of the sky from the outermost of the three TRAPPIST exoplanets in the star’s habitable zone (see the 360-video below). Credit: NASA

On Wednesday, February 22nd, US space agency NASA, working with a team of European astronomers, confirmed no fewer than seven extra-solar planets are orbiting a star some 39 light years away – with three of them within the so-called “Goldilocks zone” of habitability.

The star in question is TRAPPIST-1, named for the instruments used in its discovery, the Transiting Planets and Planetesimals Small Telescope (TRAPPIST),  and more formally known as 2MASS J23062928-0502285. Regular readers of my Space Sunday column might remember that I referred to the system back in November 2016, whilst discussing the James Webb Space Telescope and the hunt of exoplanets. The NASA announcement, which coincides with the publication of a new paper by the TRAPPIST team, adds dramatic new information to the distant star system.

The first two of the planets orbiting the star were located in May 2016, after the TRAPPIST team had studied the results of a continuous series of observations of the star between September and December 2015 using the telescope, located at the European Southern Observatory’s (ESO) La Silla Observatory in Chile.

Artist’s concept showing what each of the TRAPPIST-1 planets may look like, based on available data about their sizes, masses and orbital distances. Credit: NASA

Artist’s concept showing what each of the TRAPPIST-1 planets may look like, based on available data about their sizes, masses and orbital distances. Credit: NASA

What was intriguing about the two world was that not only were both within the so-called “Goldilocks zone” of their parent planet, where conditions might be “just right” for life to start, but both were roughly comparable to Earth in size, and therefore likely solid bodies, and spectral analysis suggested both have atmospheres.

A third planet, TRAPPIST-1d was also discovered the the same time, but it was behaving oddly. This prompted a further extended period of observation between September and October 2016, using both the ESO’s ground-based Very Large Telescope, and the Spitzer Space Telescope. This work revealed at “TRAPPIST-1d” was not one, but three worlds, again, all roughly in the Earth-sized category. Spitzer’s data additionally revealed two more planets of roughly the same size, taking the total to seven. Following this, Hubble turned its attention on the planets, looking for signs of hydrogen and helium – the chemical signatures that would indicate if any of them might be gas giants. It found none, further confirming they are likely rocky in nature.

The size, mass and density of these telluric worlds were obtained by measuring the periodic dips in TRAPPIST-1’s luminosity as a result of each of the planets passing in front of it. This allowed the international team studying the system to further assess whether each world was rocky, icy, or gaseous and determine which might be habitable.

trappist-1-3

Via: Space.com. Click for full size

TRAPPIST-1 is an ultra-cool red dwarf star only slightly larger than the planet Jupiter, and about 2,000 times dimmer than the sun.

Such stars, designated Class M, are the most frequent type of star in the Universe – making up an estimated 70% of stars in our galaxy alone. However, they do not radiate energy like our own sun, instead they are very volatile; all activity within them is entirely convective in nature, giving rise to massive stellar flares.

Given TRAPPIST-1 is so small, all of its planets orbit in very close proximity to it – closer than Mercury is to the Sun (the nearest orbits its parent star once every 1.5 terrestrial days, and the outermost, about once every 20 terrestrial days). This makes them very vulnerable to violent outbursts by the star, and could affect their surface conditions and their ability to retain an atmosphere.

This close proximity also means all of the planets are tidally locked – they always have the same side facing their sun. Thus they all are likely to have extremes of temperature, and those with an atmosphere are likely to have quite extreme weather as well. However – and conversely – it also means they could have the potential for liquid water to exist on their surfaces.

The innermost of the three planets in the habitable zone, TRAPPIST-1e, is very close in size to Earth, and receives about the same amount of light as Earth does, and may well have similar day time temperatures. The middle planet of the three, TRAPPIST-1f, meanwhile, might be a water rich world, also roughly the same size as Earth. It has a 9-day orbit, and receives about the same amount of light from its sun as Mars does from our own.

Another artist's impression of how the TRAPPIST system might look from the surface of one of the worlds - assuming they have liquid water present

Another artist’s impression of how the TRAPPIST system might look from the surface of one of TRAPPIST-1f, the middle one of the three planets in the star’s habitable zone – assuming it has liquid water present. Credit: NASA

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