Space Sunday: rovers, robots, rockets and space stations

NASA’s Mars Science Laboratory rover Curiosity has begun the steep ascent of an iron-oxide-bearing ridge that’s grabbed scientists’ attention since before the mission arrived on Mars in 2012.

“Vera Rubin Ridge”, previously referred to as “Hematite Ridge”, stands prominently on the north-western flank of Mount Sharp, resisting erosion better than the less-steep portions of the mountain below and above it.

“We’re on the climb now, driving up a route where we can access the layers we’ve studied from below,” said Abigail Fraeman, a Curiosity science-team member. As we skirted around the base of the ridge this summer, we had the opportunity to observe the large vertical exposure of rock layers that make up the bottom part of the ridge. But even though steep cliffs are great for exposing the stratifications, they’re not so good for driving up.”

The ascent to the top of the ridge will take the rover through a 65 metre (213 ft) change in elevation, which is being achieved through a series of drives which started in early September 2017, and which will cover a distance of around 470 metres (1542 ft).

Vera Rubin Ridge mosaic of 70 images captured by Curiosity’s Mastcam telephoto lens on August 13th, 2017. The layering of the ridge can clearly be seen. Credit: NASA/JPL / MSSS

The ridge is of particular interest to scientists not only for its erosion resistant composition, but also because the rock of the ridge exhibits fine layering, with extensive bright veins of varying widths cutting through the layers. Orbital spectrometer observations have revealed the iron-oxide mineral hematite shows up more strongly at the ridge top than elsewhere on lower “Mount Sharp”, including locations where Curiosity has already found the mineral. It is hoped that a detailed study of the ridge will reveal why it has been so resistant to erosion and whether this is related to the high concentrations of hematite in the rock. Answering these questions could further reveal information on past environmental conditions within Gale Crater.

“The team is excited to be exploring Vera Rubin Ridge, as this hematite ridge has been a go-to target for Curiosity ever since Gale Crater was selected as the landing site,” said Michael Meyer, lead scientist of NASA’s Mars Exploration Programme at the agency’s Washington headquarters.

A monochrome image of “Vera Rubin Ridge” captured using the imager on Curiosity’s ChemCam instrument shows sedimentary layers and fracture-filling mineral deposits. ChemCam’s telescopic Remote Micro-Imager took the 10 component images of this scene on July 3rd, 2017, from a distance of about 377 feet. Credit: NASA/JPL / CNES / CNRS / LANL / IRAP / IAS / LPGN

Curiosity Project Scientist Ashwin Vasavada of JPL added, “Using data from orbiters and our own approach imaging, the team has chosen places to pause for more extensive studies on the way up, such as where the rock layers show changes in appearance or composition. But the campaign plan will evolve as we examine the rocks in detail. As always, it’s a mix of planning and discovery.”

In the meantime, and in the saw-sawing of evidence concerning the past habitability of Mars, a team from the Los Alamos National Laboratory (LANL) has discovered evidence of boron on Mars, adding weight to the pro-life side of the argument.

A key building block of modern life is ribonucleic acid (RNA), which requires the sugar ribose. Like all sugars, ribose is unstable and quickly dissolves in presence of liquid, particularly water. However, when boron is dissolved in water it becomes borate, which acts as would act as a stabilising agent of ribose, keeping the sugar together long enough so that RNA can form.

“Borates are one possible bridge from simple organic molecules to RNA,” Patrick Gasda, the lead author of the LANL paper outlining the discovery. “Without RNA, you have no life. We detected borates in a crater on Mars that’s 3.8 billion years old, younger than the likely formation of life on Earth.”

An artist’s impression of how the lake in Gale Crater may once have looked. The central “island” is the impact peak and humped formation of “Mount Sharp”. Credit: Kevin M. Gill

The mineral was detected by Curiosity’s ChemCam instrument, a joint development by LANL the French space agency, the National Center of Space Studies (CNES). It was found in veins of calcium sulphate minerals located in the Gale Crater, indicating it was present in Mars’ groundwater and was preserved with other minerals when the water dissolved, leaving behind rich mineral veins.

Curiosity has already confirmed that Gale Crater was home to a series of lakes, and the LANL findings add weight to the potential these lakes could have had life in them at a time when it would have experienced temperatures ranging from 0 to 60 ° C (32 to 140 °F) and had a pH level that would have been neutral-to-alkaline.

OSIRIS-REx Swings by Earth

Just over a year ago, on September 8th, 2016, NASA’s Origins, Spectral Interpretation, Resource Identification, Security – Regolith Explorer (OSIRIS-REx) lifted-off from Space Launch Complex 41 at Cape Canaveral Air Force Station, at the start of a journey which will carry it a total of 7.2 billion kilometres (4.5 billion miles) to gather samples from the surface of an asteroid and return them to Earth for study (see my previous reports here and here).

On September 22nd, 2017, the spacecraft returned to the vicinity of Earth – albeit it briefly –  to gain the gravity assisted speed boost it needs in order to complete its journey to the carbon rich asteroid Bennu, from which it will gather samples.

A graphic issued ahead of the OSIRIS-REx fly-be on Friday, September 22nd. Credit: NASA’s Goddard Space Flight Centre / University of Arizona

In making the flyby, the spacecraft came to within 17,000 km (11,000 mi) of Earth, approaching at a speed of around 30,400 km/h (19,000 mph) and passing over Australia and Antarctica, gaining a velocity boost of around  13,400 km/h (8,400 mph) as it accelerated back out into the solar system. The fly-by also curved the probe’s course onto an intercept trajectory with Bennu, which it will reach in October 2018. During the operation, OSIRIS-REx performed a science campaign, collecting images and data from Earth and the Moon, which also allowed the science team to check and calibrate the probe’s suite of science instruments.

Bennu is roughly 450 metres (1,614-ft) in diameter, and its solar orbit carries it across that of the Earth  every six years. It is carbon rich, which is of significant interest to scientists because carbonaceous material is a key element in organic molecules necessary for life, as well as being representative of matter from before the formation of Earth. Organic molecules, such as amino acids, have previously been found in meteorite and comet samples, indicating that some ingredients necessary for life can be naturally synthesised in outer space.

On reaching Bennu, OSIRIS REx will “fly” alongside the asteroid for some 12 months, surveying and studying it and imaging points of interest as possible candidates for a daring “touch and go” sample gathering mission, when it will collect between 60 and 2000 grams (2–70 ounces) of material. If all goes well, the probe will depart Bennu in March 2021, arriving back at Earth in September 2023, when the sample will be parachuted down for scientists to study.

A secondary reason for visiting Bennu is that, like many Near-Earth Asteroids (NEAs) there is a slim chance it might strike our planet towards the end of the 22nd Century. An analysis of the thermal absorption and emissions of the asteroid will allow scientists to better predict its future orbits and the real potential for such a collision, and could help determine the actual risk of other NEAs striking Earth.

NASA to Push Back EM-1?

NASA will be publishing an updated schedule for the Orion / Space Lunch System (SLS) on October 1st, 2017. In it, the agency is expected to indicate the first, uncrewed, flight of the Orion Multi-Purpose Crew Vehicle atop the new Space Launch System rocket will now not take place until 2019. Called EM-1, for Exploration Mission 1, which would have been the first flight of an SLS booster and place an Orion  / service Module unit on a flight around the Moon and back, this mission had originally been expected to take place in December 2017.

Documents circulated within the US space agency have already suggested the Em-1 flight should be delayed until no earlier than December 2019. These cite assorted factors, including delays in the development of the Orion Service Module, which is being supplied by the European Space Agency, and recent natural events: NASA’s Michoud Assembly Facility in New Orleans was recently hit by a tornado, and  Hurricanes Harvey and Irma led to shut-down of NASA’s Johnson and Kennedy Space Centres, both of which suffered some damage.

An artist’s impression of the roll-out of the SLS / Orion from the Vehicle Assembly Building at Kennedy Space Centre. Credit: NASA

However, the agency was already looking to revise the Orion / SLS schedule after a report from the U.S. Government Accountability Office (GAO) earlier this year indicated the time line for SLS development was far too aggressive in trying to meet a December 2017 launch date, and mistakes were occurring – such as a welding fault on one of the rocket’s fuel tanks – as a result.

The delay to EM-1 is likely to have a knock-on effect with the first crewed flight of Orion, dubbed Exploration Mission 2 (EM-2). It is anticipated that this will likely slip from August 2021 to at least June 2022. However, some delay was already expected for this mission to allow time for upgrades to be carried out at the Pad 39B launch facilities at Kennedy Space Centre to cater for launching the SLS with a more powerful upper stage then the initial variant of the rocket (Block 1) will use.

Tianzhou-1: Mission End

China’s first cargo spacecraft, Tianzhou-1 (“Heavenly Ship 1”), separated from the country’s (currently uncrewed) Tiangong-2 (“Heavenly Palace 2”) space laboratory on Sunday, September 17th, marking the start of the final phase of its mission.

Launched in April 2017, the Tianzhou-1 automated vehicle is the first in a line of vehicles vital to China’s ambitions to build and operate their own space station in Earth orbit, with work expected to commence in 2019. The Tianzhou vehicles will fly up to 6.5 tonnes equipment, consumables and fuel at a time to the 60-tonne Chinese space station, once it becomes operational in the early 2020s.

An artist’s impression of Tianzhou-1 (left) docked with the slightly larger Tiangong-2 orbital laboratory. Credit: CMSE

Since its launch, the Tianzhou-1 vehicle has carried out three rendezvous and docking procedures with  Tiangong-2 as dress rehearsals for operations with the new space station. These manoeuvres have also involved transferring fuel (required by the laboratory’s manoeuvring thrusters). The last of these rendezvous took place on earlier in September in what was called a “fast docking” manoeuvre, completing the rendezvous and docking entirely automatically in around 6.5 hours, rather than the 2 days for the two prior dockings in April and June 2017. A final fuel transfer operation was carried out between the resupply vehicle and orbital laboratory on Saturday, September 16th.

Between these rendezvous operations, Tianzhou-1 operated independently of  Tiangong-2, carrying out a range of automated flight manoeuvres to test its capabilities, and performing a range of science activities. After separating from the laboratory vehicle on September 17th,  Tianzhou-1 took up its own orbit around Earth at an altitude of 400 km for several days. Then, on Friday, September 22nd, the 10.6 metre (35 ft) long vehicle was commanded to perform two de-orbit burns, causing it to drop back into the denser atmosphere, where it burnt up.

Artist’s impression of the planned Chinese space station complex. Credit: CCTV

Originally, it had been anticipated that a second crew would visit Tiangong-2 following the Tianzhou-1 tests. However, this now appears not to be the case. Instead, China will focus on their space station, starting with the launch of the first module – the Core Cabin module, dubbed “Tianhe 1” (““Harmony of the Heavens 1”).

This is expected to be followed by a Tianzhou resupply vehicle (Tianzhou-2); only then will a crew fly into space, aboard the Shenzhou 12 spacecraft, which will also dock with the station’s core module. Overall, it is expected the station will be completed by 2022, with two Laboratory Cabin Modules for scientific work being added in 2021 and 2022 respectively. The Chinese station will be somehat smaller than the ISS – massing 60 tonnes compared to the ISS’s 450 tonnes, and will roughly equate to the Soviet / Russian Mir space station.

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