Space Sunday: Mars rover round-up

Curiosity, NASA’s Mars Science Laboratory (MSL) continues its exploration and examination of “Vera Rubin Ridge” on the slopes of “Mount Sharp”.

Most recently, star- and swallowtail-shaped tiny, dark bumps in fine-layered bright bedrock have been drawing the attention of the rover’s science team due to their similarity to gypsum crystals formed in drying lakes on Earth – although multiple possibilities for the features are being considered alongside their potential for being formed as a result of water action.

The features pose a number of puzzles: where they formed at the same time as the layers of sediment in which they sit, or were formed later as a result of some action? Might they have been formed inside the rock sediments of “Mount Sharp” and exposed over time as a result of wind erosion? Do they contain the mineral that originally crystallised in them, or was it dissolved away to be replaced by another? Answering these questions may point to evidence of a drying lake within Gale Crater, or to groundwater that flowed through the sediment after it became cemented into rock.

“Vera Rubin Ridge” stands out as an erosion-resistant band on the north slope of lower Mount Sharp inside Gale Crater. It was a planned destination for Curiosity even before the rover’s 2012 landing on the crater floor near the mountain. The rover began climbing the ridge about five months ago, and has now reached the uphill, southern edge. Some features here might be related to a transition to the next destination area uphill, which is called the “Clay Unit” because of clay minerals detected from orbit.

In addition to the deposits, the rover team also is investigating other clues on the same area to learn more about the Red Planet’s history. These include stick-shaped features the size of rice grains, mineral veins with both bright and dark zones, colour variations in the bedrock, smoothly horizontal laminations that vary more than tenfold in thickness of individual layers, and more than fourfold variation in the iron content of local rock targets examined by the rover.

A mineral vein with bright and dark portions distinguishes this Martian rock target, called “Rona,” near the upper edge of “Vera Rubin Ridge” on Mount Sharp. The MAHLI camera on NASA’s Curiosity Mars rover took the image after the rover brushed dust off the grey area, roughly 5cm by 7.5 inches. Click for full size. Credit: NASA/JPL / MSSS

The deposits are about the size of a sesame seed. Some are single elongated crystals. Commonly, two or more coalesce into V-shaped “swallowtails” or more complex “lark’s foot” or star configurations. They are characteristic of gypsum crystals, a form of calcium sulphate which can form when salts become concentrated in water, such as in an evaporating lake.

“These tiny ‘V’ shapes really caught our attention, but they were not at all the reason we went to that rock,” said Curiosity science team member Abigail Fraeman of NASA’s Jet Propulsion Laboratory. “We were looking at the colour change from one area to another. We were lucky to see the crystals. They’re so tiny, you don’t see them until you’re right on them.”

“There’s just a treasure trove of interesting targets concentrated in this one area,” Curiosity Project Scientist Ashwin Vasavada of NASA’s Jet Propulsion Laboratory, adds. “Each is a clue, and the more clues, the better. It’s going to be fun figuring out what it all means.”

In January, Curiosity examined a finely laminated bedrock area dubbed “Jura”, thought to result from lake bed sedimentation, as has been true in several lower, older geological layers Curiosity has examined. This tends to suggest the crystals formed as a lake in the crater evaporated. However, an alternate theory is that they formed much later, as a result of salty fluids moving through the rock during periodic “wet” bouts in the planet’s early history. This would again be consistent with features previous witnessed by Curiosity in its past examination of geological layers, where subsurface fluids deposited features such as mineral veins.

The surface of the Martian rock target in this stereo, close-up image from the Curiosity rover’s MAHLI camera includes small hollows with a “swallowtail” shape characteristic of gypsum crystals. The view appears three-dimensional when seen through blue-red glasses with the red lens on the left. Click for full size. Credit: NASA/JPL / MSSS

That the deposits may have formed as a result of fluids moving down the slopes of “Mount Sharp” is pointed to by some of them being two-toned – the darker portions containing more iron, and the brighter portions more calcium sulphate. These suggest the minerals which originally formed the features have been replaced or removed by water. The presence of calcium sulphate suggests salts were suspended in any water which may have once been present in the crater. If this is the case, it could reveal more about the past history of Mars.

“So far on this mission, most of the evidence we’ve seen about ancient lakes in Gale Crater has been for relatively fresh, non-salty water,” Vasavada said. “If we start seeing lakes becoming saltier with time, that would help us understand how the environment changed in Gale Crater, and it’s consistent with an overall pattern that water on Mars became more scarce over time.”

Even if the deposits formed inside the sediments of “Mount Sharp” and were exposed over time as a result of wind erosion, it would reveal a lot about the region, providing evidence that as water became more and more scarce, so it moved underground, taking any minerals which may have been suspended within it along as well.

“In either scenario – surface or underground formation –  these crystals are a new type of evidence that builds the story of persistent water and a long-lived habitable environment on Mars,” Vasavada notes.

As well as offering further evidence of Gale Crater having once being the home of multiple wet environments, the presence of iron content in the veins and features might provide clues about whether the wet conditions in the area were favourable for microbial life. Iron oxides vary in their solubility in water, with more-oxidized types generally less likely to be dissolved and transported. An environment with a range of oxidation states can provide a battery-like energy gradient exploitable by some types of microbes.

Opportunity’s Mystery

As Curiosity explores “Vera Rubin Ridge”, half a world away, NASA’s Mars Exploration Rover (MER) Opportunity has reached 5,000 Sols (Martian days) of operations on Mars in what was originally seen as a 90-day surface mission.

A view from the front Hazard Avoidance Camera on NASA’s Mars Exploration Rover Opportunity shows a pattern of rock stripes on the ground, a surprise to scientists on the rover team. It was taken in January 2018, as the rover neared Sol 5000 of what was planned as a 90-Sol mission. Credit: NASA/JPL

Currently, Opportunity is investigating a mystery of its own: a strange  ground texture resembling stone striping seen on some mountain slopes on Earth that result from repeated cycles of freezing and thawing of wet soil. The texture has been found within a channel dubbed “Perseverance Valley” the rover is exploring in an attempt to reach the floor of Endeavour crater. This 22 km (14 mi) diameter impact crater has been the focus of Opportunity’s studies since it reached the edge of the crater in October 2011.

The striping takes the form of soil and gravel particles appearing to be organised into narrow rows or corrugations, parallel to the slope, alternating between rows with more gravel and rows with less. One possible explanation for their formation is that on a scale of hundreds of thousands of years, Mars goes through cycles when the tilt, or obliquity, of its axis increases so much that some of the water now frozen at the poles vaporises into the atmosphere and then becomes snow or frost accumulating nearer the equator and around the rims of craters like Endeavour.

Continue reading “Space Sunday: Mars rover round-up”

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A double helping of Soul to Soul in Second Life

Soul2Soul River; Inara Pey, February 2018, on FlickrSoul2Soul River – click any image for full size

In January, MiaRiche Resident dropped me a line inviting Caitlyn and I to visit Soul2Soul River, a public / private homestead region designed and operated by Minnie Blanco (Minnie Atlass). It’s actually one of two Homestead regions Minnie has landscaped and offers for both public visits and private rentals, the other being Soul2Soul Bay.  Both are inspired by part of Minnie’s native England – and as such, have a particular attraction for Caitlyn and I.

Minnie describes Soul2Soul River as a reflection of the Thames River – although those unfamiliar with the full length of Old Father Thames may not recognise this at first glance, the Thames being popularly associated with London more than anywhere else. However, as the longest river rising and flowing entirely through England, it has many faces, its youngest being in Cotswolds district of Gloucestershire where the Thames rises – and it is this which forms the inspiration for Soul2Soul River.

Soul2Soul River; Inara Pey, February 2018, on FlickrSoul2Soul River

Given that Second Life regions are relatively small, representing a decent stretch of a river running through them isn’t easy without introducing a lot of twists and turns – and potentially reducing the width of the river itself, making it less of a focus. Minnie has sought to avoid this by dividing the region into four parts split by water. This way, when exploring, one can get the feeling of looking and walking along three stretches of a single river.

A visit starts at a small village landing point which might be referred to as “classically Cotswold”. Thatched cottages sit alongside a countryside pub, overlooking a stretch of river guarded by willows and bordered by reeds and flowers. A bridge spans the water to where a footpath runs around the south side of the land, offering a riverbank walk which loops back to a path cutting over the hill to the far side, and another bridge linking to the western side of the region – which is home to one of the rental properties, so please keep privacy in mind if you cross the bridge.

Soul2Soul River; Inara Pey, February 2018, on FlickrSoul2Soul River

A second path runs along the riverbank on the far side of the river to the village, offering views back towards the bridge and pub. It’s open to the public, but be aware that again it does run around to rental properties. Further retails are scattered along river banks, all positioned so that they can enjoy a degree of privacy from one another, and with enough room between them to offer space to explore.

Soul2Soul Bay takes its inspiration from the Cornish coastline, offering a little beach bay and a village – which again forms the landing point, complete with old chapel on the hill. A track runs down the hill from the village to the beach front and the sweeping curve of the bay’s C. The sand here offers a route around the region, passing the scattered rental properties.

Soul2Soul River; Inara Pey, February 2018, on FlickrSoul2Soul Bay

Getting around on foot is easy, but for those who prefer, there is a bicycle rezzer opposite the post office (rentals office) allowing visitors to take a ride around the region’s public areas. There are also several places to sit and rest from walking or riding, including on a number of rowing boats moored in the bay and deck chairs in the sand.

Visiting both Soul2Soul regions, I admit to being a little more attracted to Soul2Soul River – but this is primarily because I have an affinity for the Cotswolds, and really enjoyed the views along the river.  The truth is both Soul2SoulRiver and Soul2Soul Bay are picturesque and make for a relaxing visit. Those looking for a home within themed regions might also find them well worth a visit, while photographers will find both regions attractive to their cameras.

Soul2Soul River; Inara Pey, February 2018, on FlickrSoul2Soul Bay

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