Category: Other Worlds and Tech

Space Sunday: of water, Apollo and space spies

Posted on by Inara Pey

CuriosityThe Curiosity rover team have released a further study showing that ancient Mars was capable of storing water in lakes over an extended period of time, and that this water was a principal component in the creation of “Mount Sharp”, the mound at the centre of Gale Crater, currently being investigated by the NASA rover.

This forms the latest in a series of reports on the subject of water on Mars and in Gale Crater to be published by the Curiosity science team, and comes almost a year after I wrote about studies released by the team which detailed how “Mount Sharp” – more formally known as Aeolis Mons – was most likely formed by sediments laid down  by successive wet period in Mars’ ancient past.

“Observations from the rover suggest that a series of long-lived streams and lakes existed at some point between about 3.8 to 3.3 billion years ago, delivering sediment that slowly built up the lower layers of Mount Sharp,” said Ashwin Vasavada, Mars Science Laboratory project scientist, discussing the new report.

In December 2014, NASA issued a report on how
In December 2014, NASA issued a report on how “Mount Sharp” was likely formed. On the left, the repeated depositing of alluvial and wind-blown matter (light brown) around a series of central lakes which formed in Gale Crater, where material was deposited by water and more heavily compressed due the weight of successive lakes (dark brown). On the right, once the water had fully receded / vanished from the crater, wind action took hold, eroding the original alluvial / windblown deposits around the “dry” perimeter of the crater more rapidly than the densely compacted mudstone layers of the successive lake beds, thus forming “Mount Sharp”

However, until Curiosity actually started studying “Mount Sharp” in detail,  the accuracy of the earlier studies couldn’t be completely verified. The latest results from the rover indicate that these wetter scenarios were correct for the lower portions of Mount Sharp, and that the filling of at least the bottom layers of the mountain occurred over a period of less than 500 million years, mostly as a result of material deposited by ancient rivers and lakes.

The new report also comes on top of confirmation that the recurring slope lineae (RSL) features seen on Mars from orbit are most likely the result of outflows of water which are occurring today. together they are reshaping some of the thinking around water on Mars – and what might have happened to it.

“What we thought we knew about water on Mars is constantly being put to the test,” said Michael Meyer, lead scientist for NASA’s Mars Exploration Programme. “It’s clear that the Mars of billions of years ago more closely resembled Earth than it does today. Our challenge is to figure out how this more clement Mars was even possible, and what happened to that wetter Mars.”

Strata at the base of
Curiosity has found plenty of evidence for water on the floor of Gale Crater, which likely took the form of one or more lakes during the wetter parts of Mars’ history, before becoming rivers and streams later. Strata at the foot of “mount Sharp” (shown above) strongly suggested water played a significant part in forming the mound, and the evidence for this being the case has continued to be revealed as the rover climbs the lower slopes

Currently, images of the flanks of the mound returned by the rover and from orbit suggest water-transported sedimentary deposition may have extended at least 150 to 200 metres (500 to 650 feet) above the crater floor, and possibly as high as 800 metres (approx 1/2 a mile). This both indicates that there was at least one standing body of water in the crater and further confirms that “Mount Sharp” was a direct result of sediments deposited by this water. Or at least, the lower slopes were; there is currently little evidence for the sedimentary strata extending about the 800 metre mark, however. This has led to speculation that wind-blown deposits are responsible for the upper reaches of the mound.

Taken together, the recent findings concerning Mars and its water suggest that the planet’s history is far more complex than had been thought. “We have tended to think of Mars as being simple,” John Grotzinger, the former project scientist for the Curiosity mission said of the latest findings.

“We once thought of the Earth as being simple too,” he continued. “But the more you look into it, questions come up because you’re beginning to fathom the real complexity of what we see on Mars. This is a good time to go back to re-evaluate all our assumptions. Something is missing somewhere.”

Pluto’s Water

The blue haze of Pluto's atmosphere
The blue haze of Pluto’s atmosphere: released on October 8th, this true colour image taken after the New Horizons spacecraft had completed its closest approach to the dwarf planet shows Pluto’s night side ringed by the blue haze of its thin atmosphere, as illuminated by the distant Sun, far away on the other side of the little world

The latest images and data to be received on Earth from NASA’s New Horizons space vehicle reveal Pluto’s atmosphere to be a rich blue in colour, and confirm that water ice exists on theplanet.

“Who would have expected a blue sky in the Kuiper Belt? It’s gorgeous,” said Alan Stern, New Horizons principal investigator as the striking image shown above was released as part of the latest batch of pictures and data to be received from the space craft and undergo processing and initial analysis.

The blue colour indicates that the haze within Pluto’s atmosphere is made up of a lot very fine of particulate matter, which scatters blue light from the Sun more easily than other colours, due to blue having a shorter wavelength (which is also the reason the sky we see here on Earth also appears blue, because that wavelength is easily scattered by the tiny particles making up our atmosphere).

In Pluto’s case, it’s thought that the particles in the atmosphere are largely tholins, created by ultraviolet radiation from the Sun breaking down the methane and nitrogen in Pluto’s upper atmosphere, allowing their molecules to gradually recombine into the more complex tholins, which draft down through the atmosphere, undergoing further changes, before eventually reaching the surface of the planet, giving it a distinctive reddish colour.

Instruments forming the Ralph suite aboard New Horizons have identified regions of exposed water ice on Pluto which occur in regions which have corresponding deposits of tholins. Quite what the relationship is between the two is unclear. The water ice deposits are shown in blue on the inset image simply for convience, and not because that's how they appear on Pluto
Instruments forming the Ralph suite aboard New Horizons have identified regions of exposed water ice on Pluto which occur in regions which have corresponding deposits of tholins. Quite what the relationship is between the two is unclear. The water ice deposits are shown in blue on the inset image simply for convenience, and not because that’s how they appear on Pluto

The discovery of water ice on Pluto has taken scientists by surprise. Not so much because it is there, but because it appears to be somehow related to areas of heavy tholin deposits. Confirmation of the presence of water ice came from data returned by the Ralph instrument suite aboard New Horizons, but just how widespread it might be isn’t clear, as it seems that it might be masked elsewhere by other surface material.

Continue reading “Space Sunday: of water, Apollo and space spies” →

Space Sunday: of Martian water, avalanches and postcards

Posted on by Inara Pey
A false-colour image of Hale Crater on Mars showing recurring slope lineae (RSL) flowing downhill, which are inferred to have been caused by contemporary flowing water, hydrated salts detected within the dark-colours RSLs tending to confirm they hypothesis they were created by free-flowing water.
A false-colour image of Hale Crater on Mars showing recurring slope lineae (RSL) features flowing downhill. Hydrated salts detected within the dark-coloured RSLs tend to confirm the hypothesis they were, and are, created by free-flowing water.

On Monday, September 28th, NASA held a special press conference which, they had promised, would “solve” a “major” mystery about Mars.

As I noted in my Space Sunday update prior to the conference, the major speculation was that the US space agency would be discussing what are called recurring slope lineae (RSL) features on Mars.

RSLs have been the subject of intense debate and discussion since 2011, when an undergraduate called Lujendra Ojha published the first in a series of papers on their presence on Mars.  In essence, they are ridges and rills which appear on the slopes of hills and craters, notably in the equatorial regions of Mars. The significance here being that on Earth, identical features are always the result of free-flowing water.

Given that it is known that Mars once supported liquid water on its surface, the presence of these features wouldn’t be that exceptional were they part of the ancient landscape. However, as the “recurring” in the title suggests, the Martian RSLs appear to be active – recurring frequently, sometimes on the seasonal basis. renewing and growing, with new ones also being periodically created.

Two images studied by Ojha showing the flank of the same crater and showing what appear to be active RSLs.
Two images studied by Ojha showing the flank of the same crater. On the left, from 2007, a number of older RSLs, faded due to dust deposits, appear with a relatively new, dark RSL. By 2012 (on the right), that RSL feature has also faded, but a further new one has appeared

Given the overall similarities between RSLs seen on Mars and those seen on Earth, particularly in Antarctica, the common belief has been that liquid water is responsible for the features on Mars. If true, then it would indicate two things.

The first would be that Mars would appear to have a subsurface water table of some description – which would be consistent with the idea that as the planet lost its atmosphere, whatever water remained on the surface may have retreated underground. The second is that it would seem to indicate that Mars is still in some way geologically active, with some mechanism at work forcing this water to the surface and creating these sudden, if short-lived outflows.

The NASA conference coincided with the publication of another paper in Nature Geoscience by Ojha and his colleagues. both pointed directly to water being the cause of the Martian RSLs. In particular, they both report that spectral analysis of some of the more recent and broader RSL channels shows they are rich in hydrated salts, which strongly indicates the presence of water. These salts are consistent with the chemical signatures of magnesium perchlorate, magnesium chlorate and sodium perchlorate.

This is significant because the presence of perchlorate deposits in water can work to prevent that water freezing solid in the kind of summer daytime temperatures – around -23C (-10F) – often experienced in the regions where these RSLs are found. Thus, if held in suspension, they would create a watery brine capable for fluid motion, and which, if released in significant enough amounts, could give rise to the RSLs prior to the water itself sublimating rapidly into the tenuous Martian atmosphere, leaving the hydrated deposits behind.

Nepalese born
Nepalese born Lujendra Ojha is the student who started the investigations into RSLs and their possible relation to free-flowing liquid water on Mars (image: The Himalayan)

The conclusion is that it is indeed liquid water that is causing these RSLs on Mars, and that this water is in a liquid, rather than solid state, at least during certain periods, such that it can be forced to the surface.

However, all is still not entirely clear – something which tends to cast a shadow on the idea of a “mystery” having been “solved”. For one thing, if the RSL rills are below a certain width, they are entirely devoid of any hydrated deposits. This could mean that some other process is involved in their formation, which has yet to be determined. Further, the mechanism which is actually responsible for forcing the water to the surface a creating the outflow which result in these RSLs is still unknown.

Continue reading “Space Sunday: of Martian water, avalanches and postcards” →

High Fidelity: September update and things to come

Posted on by Inara Pey

HF-logoThe September newsletter from High Fidelity appeared at the end of that month, with Chris Collins highlighting some of the work that has been going on of late, providing an update on particle effects, procedural textures and – most interestingly – avatar kinematics and in-world object manipulation using an avatar’s hands and via suitable controllers.

Procedural textures allow for complex, algorithm based textures to be created using tools such as ShaderToy and used directly within High Fidelity. Brad Davis has created a video tutorial on procedural entities which Chris references in the newsletter, the write-up also follows a short video released on the High Fidelity  you Tube channel which briefly demonstrates procedural textures in HiFi.

However, it is the object manipulation that’s likely to get the most attention, together with avatar kinematics and attempts to imply a force when moving an object.

In terms of avatar kinematics, Chris notes:

In 2016, when the consumer versions of the HMD’s are released, you are also going to be using a hand controller. It is therefore important that we can make your avatar body simulate correct movement with the hand data that we receive back from the controllers.

The results are shown in the newsletter in the form of  some animated GIFs. In the first, Chris’ avatar is shown responding to a Hydra controller for hand movements and echoing his jaw movements. The second demonstrates object manipulation, with Chris’ avatar using its hand to pick up a block from an in-world game, echoing Chris’ motions using a hand-held controller.

Manipulating in-world objects in High Fidelity via an avatar's hands and a set of controllers (image: High Fidelity)
Manipulating in-world objects in High Fidelity via an avatar’s hands and a set of controllers (image: High Fidelity)

The animation in picking up the block may not be entire accurate at this point in time – the block seems to travel through the avatar’s thumb as the wrist is rotated – but that isn’t what matters. The level of manipulation is impressive, and it’ll be interesting to see if this might be matched with things like feedback through a haptic style device, so that users can really get a sense of manipulating objects.

The object manipulation element, together with attempts to imply a force when moving objects in-world which make up a core part of the video accompanying the newsletter (and which is embedded below). Again, this really is worth watching, as the results are both impressive, and illustrate some of the problems High Fidelity are trying to solve in order to give virtual spaces greater fidelity.

Coupling object manipulation with implied force opens up a range of opportunities for things like in-world games, physical activities, puzzles, and so on. There’s also potential for learning and teaching as well, so it’ll be interesting to see how this aspect of the work develops.

The newsletter also promises that we’ll be seeing some further VR demo videos from High Fidelity in October, so keep an eye out for those as well.

Microsoft acquires Havok, the Second Life physics engine

Posted on by Inara Pey
Haovk: acquired by Microsoft
Haovk: acquired by Microsoft

News has been spreading about Microsoft’s acquisition of the Havok physics engine from Intel for an undisclosed sum.

Ciaran Laval was perhaps the first SL blogger to report the news, which has been featured on the likes of the IGN website, Engadget, Venture Beat’s Gamesbeat, and other on-line tech news outlets.

For those unfamiliar with Havok, it is it the physics engine that drives a vast number of computer and console games. It allows these games to simulate effects such as gravity, friction, collisions between objects and other natural forces, without the need for them to be individually coded and accounted for on a per-game basis.

Within Second Life, Havok is used for the purposes of physics simulation, and Havok sub-libraries licensed by the Lab are also used in such aspects of the platform as pathfinding (remember that?) and the official mesh uploader.

As well as being used for in-world physics, Havok libraires are also used within the official viewer (and TPVs which have signed a sub-licence agreement) to handle aspects of pathfinding and mesh uploads (shown here)
As well as being used for in-world physics, Havok libraries are also used within the official viewer (and TPVs which have signed a sub-licence agreement) to handle aspects of pathfinding and mesh uploads (shown here)

Microsoft has been a Havok partner for a number of years, and as a part of the acquisition has promised to allow developers elsewhere to continue to use it, stating:

Havok is an amazing technology supplier in the games industry and the leading real-time physics creator. We saw an opportunity to acquire Havok to deliver great experiences for our fans. Throughout the company’s history, they’ve partnered with Activision, EA, Ubisoft, Nintendo, Sony, Microsoft and many others to create more than 600 games including Halo, Assassin’s Creed, Call of Duty, Destiny, Dark Souls and The Elder Scrolls.

Microsoft’s acquisition of Havok continues our tradition of empowering developers by providing them with the tools to unleash their creativity to the world.   We will continue to innovate for the benefit of development partners.

But, if a long-term partner with Havok, why take the step of purchasing it outright? Jeff Grubb, over at Gamesbeat takes a lead from a part of Microsoft’s announcement of the acquisition, to suggest the company are looking a the potential for cloud-based physics capabilities within multi-player games, as recently demonstrated in the upcoming Crackdown 3 sandbox-style third-person shooter title:

For that open-world crime game’s multiplayer mode, Microsoft is enabling players to go in and destroy skyscrapers and everything else in the world. That mode is only possible through the power of Azure, which means Crackdown 3 developers Sumo Digital and Cloudgine are building a cloud-based destruction engine that probably runs on Havok. Once that’s built, and now that Microsoft owns Havok, it could potentially license that destruction engine out to other developers.

In August, IGN had a demonstration of these capabilities within Crackdown 3, and the results are impressive:

It’s unlikely the Microsoft’s acquisition of Havok will have any immediate or medium-term inpact on Second Life. As it is, the platform currently uses the Havok  2011.2, and so far as has been indicated at various in-world meetings, there are no public plans to update the engine at the moment. Longer-term, it will be interesting to see if / how any new / additional capabilities brought to the engine might come to be deployed in Second Life and / or “Project Sansar” (assuming Havok might be the physics engine used with that platform, something that the Lab has not as yet revealed).

Space Sunday: of blood moons, Mars, Pluto and Ceres

Posted on by Inara Pey
A lunar eclipse "blood moon" seen Idaho, December 2011 (image: Matt Mills / Reuters)
A lunar eclipse “blood moon” seen Idaho, December 2011 (image: Matt Mills / Reuters)

The night of Sunday 27th / Monday 28th September  promises a very special astronomical event for those fortunate enough to have clear skies overhead and are willing to stay up late (in the UK and Europe). It will see a total lunar eclipse take place at the time when the Moon reaches perigee, its closest approach to Earth in its orbit and giving rise to both a so-called “supermoon” and a “Blood Moon”.

A “supermoon” occurs when a full moon coincides with the time when the Moon is nearing its minimum distance to Earth, a distance of roughly 363,000 kilometres (226,875 miles), leading to it appearing 7-8% larger than when seen as a full Moon at other points in its orbit. A “blood moon” is the result of the Earth’s atmosphere, lying between the Sun and Moon, scatter blue light more strongly than red, so the latter reaches the Moon more strongly, giving it a reddish-brown colour when seen from Earth.

A total lunar eclipse occurs when the Sun, Earth and Moon are lined up so that th Earth is between the Sun and Moon, and the later sits within the Earth's shadow
A total lunar eclipse occurs when the Sun, Earth and Moon are lined up so that the Earth is between the Sun and Moon, and the latter sits within the Earth’s shadow (image: NASA)

Lunar eclipses are not that rare – this one will be the second of 2015, for example. However, “supermoons” are somewhat rarer. The last was in 1982, and the next will not be until 2033. So, if you want to see a really big blood moon, and you live in Western Europe, West Africa, the Eastern side of the USA and Canada or south America, then the 27th / 28th September is the night to do so. People further afield – eastern Asia, the middle east, eastern Europe and the western sides of Canada, the USA and South America will see a partial eclipse.

In the UK, the period of eclipse will start at around 01:00 BST (00:00 GMT) on the morning of Monday, 28th September, and run through until around 05:00 BST (04:00 GMT). That’s from 20:00 through to around 01:00 EDT in the USA / Canada, and 02:00 through 06:00 CET in Europe).

A total lunar eclipse and the gradual change in the Moon’s colour as seen from Earth which sees total lunar eclipses sometimes referred to as “blood moons” – the result of sunlight passing through the Earth’s atmosphere and striking the Moon’s surface (animation: Wikipedia)

The eclipse brings to a close what is referred to as a “tetrad” of total lunar eclipses – that is, four occurring “back-to-back”, with no partial eclipses between them, the first of which occurred in April 2014 and the “middle two” in October 2014 and April 2015. Some have a misguided view that this “tetrad” as being of particular significance because such events are “rare”, and this particular one started on the Passover.

However, while there can be long periods of time between occurrences of tetrads, they can also pop-up relatively frequently. For example, this century will see a total of nine tetrads occur, the first having taken place in 2003/4. Nor is the fact that this particular series started on the Passover particularly unusual; there have been eight tetrads so far coinciding with Passover since the first century AD.

So, if you are in a position to see the eclipse, you can leave the tinfoil hat on the table and step outside quite safely. Totality should occur around two hours after the eclipse starts (e.g. 03:00 BST in the UK / 04:00 CET, 22:00 EDT on the 27th September), and that’s the best time to enjoy the blood moon in all its glory.

The eclipse will also give NASA the chance to measure the full range of temperature variations during  such an event. This will be done by the Lunar Reconnaissance Orbiter (LRO), a solar-power vehicle which has been observing the Moon since 2009.

Normally during an eclipse, the LRO has most of its systems powered down to reduce the load placed on the battery systems. However, mission controllers are confident they will be able to run an instrument which will allow it to accurately measure the amount of heat loss the surface of the Moon experiences when inside the Earth’s shadow, further helping them to understand the composition of the Moon’s regolith and its function as an insulator.

Continue reading “Space Sunday: of blood moons, Mars, Pluto and Ceres” →

Space Sunday: see Pluto’s mountains and the size of the Solar System

Posted on by Inara Pey
Back lit by the sun: Pluto's hazy atmosphere seen from just 18,000km (11,000 miles) and 15 minutes are the point of closest approach to the planet by the New Horizons spacecraft on July 14th, 2015. To the upper right of the planet can be seen the icy expanse of "Sputnik Planum", bordered below and to the left by tall mountains, and to the right by what appears to be glacial outflows. Image courtesy of NASA / JHU / APL,
Backlit by the Sun: Pluto’s hazy atmosphere seen from just 18,000km (11,000 miles) and 15 minutes are the point of closest approach to the planet by the New Horizons spacecraft on July 14th, 2015. To the upper right of the planet can be seen the icy expanse of “Sputnik Planum”, bordered below and to the left by tall mountains, and to the right by what appears to be glacial inflows. Image: NASA / JHUAPL / SwRI (click for full size)

Just when you thought images of Pluto returned by the New Horizons spacecraft could get any more awe-inspiring, NASA / JHU  APL release a set of raw images that are utterly stunning.

The images come from the wide-angle Ralph/Multispectral Visual Imaging Camera (MVIC) on the space craft and were captured just 15 minutes after the vehicle reached is point of closest approach to the little world, and thus from a distance of just 18,000 km (11,000 miles) from Pluto.

The stunning vistas presented in the image show the ice plains of “Sputnik Planum” bordered to the left and from below by Pluto’s huge mountain ranges, informally named Hillary and Norgay, Montes after the first partnership to successful reach the summit of Mt. Everest here on Earth. All of this is dramatically backlit by sunlight reflected through Pluto’s hazy atmosphere to create a wonderful scene said to be reminiscent of views of the Antarctic viewed from space or very high altitude.

A closer view: In this image just 380 km (230 miles) across, shows "Sputnik Planum" bordered to the west by towering mountains reaching up to 3,500 metres (11,000 ft) in altitude. In the foreground sit the informally-named Norgay Montes, and on the skyline to the top and left of the image, the Hilary Montes
A closer view: in this image just 380 km (230 miles) across, shows “Sputnik Planum” bordered to the west by towering mountains reaching up to 3,500 metres (11,000 ft) in altitude. In the foreground sit the informally named Norgay Montes, and on the skyline to the top and left of the image, the Hillary Montes. Image: NASA / JHUAPL / SwRI (click for full size)

However, the images aren’t just notable for the panoramic beauty; they actually reveal a lot about what is happening in the Plutoian atmosphere. Because of the back lighting from the Sun, the high-resolution MVIC has revealed just how complex Pluto’s atmosphere is, comprising multiple layers of nitrogen and other gases rising to around 100 km (60 mi) above Pluto’s surface (and visible as a banding in the images above).

“In addition to being visually stunning, these low-lying hazes hint at the weather changing from day-to-day on Pluto, just like it does here on Earth,” said Will Grundy, lead of the New Horizons Composition team from Lowell Observatory, Flagstaff, Arizona.

What is also exciting the science team is evidence within the images for Pluto having a complex “hydrological” cycle which seems to be comparable in some ways to that found on Earth – only on Pluto, it involves nitrogen ice, rather than water ice.

When compared with images captured as New Horizons approached Pluto, the MVIC images further suggest that the regions eastward of “Sputnik Planum” appear to have been encroached over time by ices and material possibly evaporated from the surface of “Sputnik Planum” to be deposited on the higher lands as a new ice blanket, which in turn appears to have formed glacial formations flowing back into “Sputnik Planum”.

Glacial flow on Pluto: deposits of frozen nitrogen which have accumulated on the uplands on the right side of this 630 km (390 mi) wide image has formed glacial flows leading from the uplands beck into "Sputnik Planum" draining from Pluto’s mountains onto the icy plain through the valley system indicated by the red arrows (the valleys average between 3 and 8 km (2 and 5 mi) in width). In the meantime, the ice of the plain appears to be flowing outwards and towards the uplands, as indicated by the blue arrows. Image: NASA/JHUAPL/SwRI.
Glacial flow on Pluto: deposits of frozen nitrogen which have accumulated on the uplands on the right side of this 630 km (390 mi) wide image has formed glacial flows leading from the uplands beck into “Sputnik Planum” draining from Pluto’s mountains onto the icy plain through the valley system indicated by the red arrows (the valleys average between 3 and 8 km (2 and 5 mi) in width). In the meantime, the ice of the plain appears to be flowing outwards and towards the uplands, as indicated by the blue arrows. Image: NASA / JHUAPL / SwRI (click for full size)

“We did not expect to find hints of a nitrogen-based glacial cycle on Pluto operating in the frigid conditions of the outer solar system,” said Alan Howard, a member of the mission’s Geology, Geophysics and Imaging team from the University of Virginia, Charlottesville. “Driven by dim sunlight, this would be directly comparable to the hydrological cycle that feeds ice caps on Earth, where water is evaporated from the oceans, falls as snow, and returns to the seas through glacial flow.”

To Scale: The Solar System

We’re all familiar with the idea that the solar system is so vast, that it is almost impossible to show the Sun and the major planets proportional to one another and at a scale where all the later are both visible and have orbits which can be adequately encompassed in an easily viewable space.

1972: The Blue Marble (click to enlarge)

Obviously, some models do exist; the Lowell Observatory in Arizona, USA, for example, has a walk that allows visitors to travel from the sun and by each of the planets, but it’s not always easy to clearly grasp the sheer scale of things. The same goes for digital models (and a few have been built within virtual worlds like Second Life).

With this issue of scale and proportion in mind, Wylie Overstreet and Alex Gorosh set out to produce a scale model of the solar system that might help people understand just how vast our planetary back yard is when looked at on a human scale.

They started with a blue marble to represent the Earth, echoing the famous photograph taken on December 7, 1972, by the crew of Apollo 17 en route to the Moon and which NASA dubbed the Blue Marble.

Continue reading “Space Sunday: see Pluto’s mountains and the size of the Solar System” →