April 16th, 2015 saw NASA’s Mars Science Laboratory rover Curiosity clock-up 10 kilometres (6.25 miles) on its odometer since it arrived on Mars 30 months ago, as it continues its trek up the slopes of “Mount Sharp”, the mountain-size mound at the centre of Gale Crater.
The rover is currently making its way through a series of connected shallow “valleys” on the slops of the mound – which is more correct names Aeolis Mons – as it continues upwards and away from the “Pahrump Hills” area it spent 6 months investigating, and towards its next major science target, an area the science team have dubbed “Logan Pass”, which is still some 200 metres away from the rover at the time of writing.
While only a distance of around 550 metres separates “Logan Pass” from the upper limits of “Pahrump Hills”, the rover’s gentle progress has been the result of several stops along the way in order to further characterise the different rock types Curiosity has been encountering, and to make important observations of its surroundings as the science team try to understand the processes by which the region’s ancient environment evolved from lakes and rivers into much drier conditions.
The rover’s progress up “Mount Sharp” has so far been through the lower reaches of the transitional layers which mark the separation points between the materials deposited over the aeons to create the gigantic mound and the material considered to be common to the crater floor. These transitional layers have been dubbed the “Murray Formation”, in honour of the late co-founder of The Planetary Society, Bruce Murray, and comprise a number of different land formations, “Pahrump Hills” being one of the lowermost. Logan Pass marks the start of another, dubbed the “Washboard unit”, and which comprises a series of high-standing buttes.
As several of the MSL reports in these pages have shown, Curiosity has already found considerable evidence that Gale Crater may once have been home to environments sufficiently benign to allow for the existence of microbial life. Whether or not those microbes survived down the millennia such that they are still present in the planet’s soil today, is not something the rover is equipped to determine; however, a recent report from one of Curiosity’s science teams suggests that subsurface conditions are unfavourable to the support of microbial life.
The evidence for this comes in the form of perchlorate salts, and the effect they can have on their environment. Perchlorate was first detected in soil samples gathered by NASA’s Phoenix Mars Lander mission in 2008, while Curiosity found trace evidence for perchlorate in samples gathered early in its own mission.
What makes perchlorate interesting is that in cold temperatures, it is able to “pull” water vapour from the atmosphere and bind with it, lowering its temperature, potentially allowing it to form sub-surface brines which would be very destructive to microbial life.
It had been thought that the environmental conditions by which this might occur were limited to the near-polar regions of the planet. However, data gathered by Curiosity’s on-board weather station, called REMS (for Rover Environmental Monitoring Station) over the course of its mission suggests the night-time conditions in Gale Crater, are right for the formation of sub-surface brines throughout the year.
While no actual brines have been detected by the rover, that they could form in the soil within the crater makes the survival of any modern-day Martian microbes there potentially unlikely. Curiosity’s data further suggests that conditions suitable for the existence of sub-surface brines are common across the planet, rather than being restricted to the the near-polar regions as had originally been thought.
That sub-surface brines can occur across the planet lends weight to the 2011 argument that it is sudden outpourings of salt water that is responsible for the recurring “seasonal flows” that occur on Mars. First observed by NASA’s Mars Reconnaissance Orbiter and formally referred to as recurring slope lineae (RSL), these are dark streaks which appear on Martian slopes (such as crater walls) during the spring months, increasing an length and darkness through the summer months, before they fade and vanish over autumn / winter.
SpaceX: Falcon Almost Makes It
April saw SpaceX, the private space ventures company led by billionaire Elon Musk, make a second attempt to land a 14-story tall first stage of their Falcon 9 launcher back on Earth following a launch.
As I’ve previously reported, SpaceX is working to develop a reusable launch booster to help reduce the cost involved in launching payloads into orbit. Part of this effort involves recovering the first stage of the booster rocket, which rocket-launched space missions have traditionally discarded to fall into the ocean once this has done its work.
To achieve this, SpaceX have developed a version of the Falcon 9 rocket first stage which, after separation from the upper stage and payload, can orient itself for a vertical descent through the air, using its main engines, before deploying a set of landing legs and touching-down again under the throttled power of its engines.
The first attempt to land a Falcon 9 rocket – which currently has to be done on water due to safety reasons, but which will eventually become a land-based operation, and which used an automated floating landing platform called Just Follow The Instructions – was made in January 2015, and was foiled in the last few seconds prior to landing when the the booster ran out of hydraulic fuel and toppled over and exploded.
A second attempt had been planned to take place in February following the launch of the NOAA’s DISCOVR mission. This had to be abandoned prior to the launch when the landing platform suffered a motor failure and was unable to hold station. This was made doubly galling for SpaceX when the first stage of the booster made a textbook descent to splash-down just 10 metres from the centre of its target area.
The third attempt took place on April 14th, 2015, as a part of a mission to send an uncrewed Dragon 1 resupply vehicle to the ISS. After launch and second stage separation (the Dragon went on to reach orbit and successfully rendezvous with the space station), the 1st stage of the booster did make a successful descent to the waiting automated landing ship. Technically, it actually made a successful landing. However a stuck bi-propellant valve meant the stage landed with too much lateral velocity which thrusters at it’s top were unable to correct, and it toppled over and exploded.
Damage to the landing barge was minimal (as with the explosion following the first attempt), and it arrived back in port under tow on April 17th.
As a result of the failure, SpaceX is now seeking to be able to return the next planned attempt to land a Falcon 9 first stage to the ground, rather than trying to landing it on a floating platform. That attempt is due to come on June 19th, and the launch of the next Dragon resupply mission to the ISS. Quite where the landing will take place is unclear; the company is developing a landing complex at Florida’s Canaveral air Force Station south of the Kennedy Space Centre, but it would appear to be far too early in the development of that facility for any landing attempt to be realistically made.
Despite the failure on April 14th, Elon Musk remained in good spirits, sending a Tweet which echoes the grand designs of bond-style super villains:
All images courtesy of NASA / JPL, unless otherwise stated. video courtesy of SpaceX.