Mars has been in the news a lot this last week, thanks to both the Curiosity rover and the MAVEN orbiter.
Curiosity’s science capabilities received a boost when a upgrade to the ChemCam test system on Earth increased the number of Earth-rock geochemical samples examined by the system tripled to some 350, vastly increasing the science team’s ability to improve their interpretation of data gathered by Curiosity’s ChemCam system – the laser and telescope / camera which vaporises small amounts of rocks on Mars and them images the plasma that’s given of for chemical and mineralogical analysis.
In particular, the upgrade has allowed the science team to re-examine data the rover gathered about a site with the most chemically diverse mineral veins so far examined on Mars. Called “Garden City”, the site sits above the “Pahrump Hills” area at the foot of “Mount Sharp”, which the rover examined in detail in late 2014 / early 2015. Of particular interest to scientists were a series of raised mineral veins criss-crossing the surface of the rocks in the area.
These new Earthside capabilities have allowed the science team to better analyse the minerals within the veins and make finer distinctions between them, revealing their mineral and chemical compositions vary one to another, and also appear to vary with age.
These findings suggest that, rather than being the result of a single extended wet period in Gale Crater during which water percolated down through fissures in the rock to leave the minerals behind, the veins are the result of several individual wet periods in Mars’ ancient past. These wet periods appear to have occurred somewhat later than the more extensive wet periods which gave rise to a successive series of lakes within Gale Crater, the sediments from which form the lowest slopes of “Mount Sharp”. As such, the veins give further hints to atmospheric changes going on at a time at which Mars’ climate was undergoing extraordinary changes and fluctuations in its ancient past.
What Happened to Mars’ Atmosphere? The Answer is Blowin’ in the Wind
Atmospheric changes are also at the heart of the latest data to be analysed from NASA’s Mars Atmosphere and Volatile Evolution (MAVEN). This data, part of the mission’s long terms studies of the planet’s atmosphere and environment greatly clarifies the key role played by the solar wind in the gradual loss of Mars’ once dense atmosphere and the transition of the planet’s climate from a warm and wet environment to the cold, arid planet we see today.
The solar wind is a stream of particles, mainly protons and electrons, flowing from the Sun’s atmosphere at a speed of about 1.6 million kilometres (1 million miles) per hour. The interaction of this solar wind generates an electric field around Mars, much like a turbine on Earth generates electricity. This electric field interacts with the upper reaches of Mars’ atmosphere, accelerating the ions there and shooting them into space.
MAVEN measurements indicate that gases are being stripped away in this manner from the Martian atmosphere at a rate of about 8.6 million tonnes per day. “Like the theft of a few coins from a cash register every day, the loss becomes significant over time,” said Bruce Jakosky, MAVEN principal investigator. “We’ve seen that the atmospheric erosion increases significantly during solar storms, so we think the loss rate was much higher billions of years ago when the sun was young and more active.”
The impact of solar storms on the rate of loss from Mars’ atmosphere was directly observed by MAVEN at the start of 2015, when the planet was bracketed by a series of large-scale outpouring from the sun – the same solar activity which gave rise to the massive increase in auroral activity at that time (see my October 26th Space Sunday report).
“Solar-wind erosion is an important mechanism for atmospheric loss, and was important enough to account for significant change in the Martian climate,” Joe Grebowsky, MAVEN project scientist said of the data gathered by the mission. “MAVEN also is studying other loss processes – such as loss due to impact of ions or escape of hydrogen atoms – and these will only increase the importance of atmospheric escape.”
The Ice Volcanoes of Pluto
“It’s hard to imagine how rapidly our view of Pluto and its moons are evolving as new data stream in each week. As the discoveries pour in from those data, Pluto is becoming a star of the solar system,” said mission Principal Investigator Alan Stern of NASA’s New Horizons mission which flew by Pluto and Charon on July 14th, 2015.
In the most recent batch of images and information from the mission to be released by the New Horizons mission team are two particularly striking features, informally dubbed “Wright Mons” and “Piccard Mons”, which are believed to be the first “ice volcanoes” found on the planet.
Both are located to the south of “Sputnik Planum” on Pluto, the icy surface feature which has been the focus of many of the observations of Pluto released to date. “Wright Mons” is approximately 160 km (100 miles) wide at its base and some 4 km (13,000 feet) tall, surmounted by a crater-like depressed approximately 56 km (35 miles) across. The rim and summit of “Wright Mons” bear concentric fracturing, a feature common to volcanoes on Earth and elsewhere, leading the science team to believe it and “Piccard Mons” could have been formed by the ‘cryovolcanic’ eruption of ices from beneath Pluto’s surface.
These ice volcanoes are important, as they could indicate that Pluto was (and is) internally active, and might help yield further clues as to what, exactly, is powering it. Further evidence for active processes can also be found in the rich mix of surface ages found on the planet, which in geological terms range from ancient to intermediate to relatively young.
Crater counts undertaken on the images received to date tend to suggest some of Pluto’s surface dates to just after the formation of the planets, about 4 billion years ago. However, they also show that much of the planet – Like “Sputnik Planum” – are geologically much younger, with some perhaps having been formed within the last 10 million or so years, something which again points to the planet being an active world.
Crater counts also help give insight into the structure of Kuiper Belt itself (of which Pluto is technically a part). The lack of smaller craters on Pluto and Charon suggests that their has always been far fewer small objects within the Kuiper Belt than had been believed. If so, then it could indicate that the long-held model that large Kuiper Belt objects like Pluto, Charon, Eres and others accreted out of much smaller objects colliding and combining is inaccurate, and that the larger bodies in the Kuiper Belt formed directly at their current – or close to current – size.
It is this idea that Kuiper Belt Objects (KBOs) could have been “born large” which has given added impetus to seeing New Horizons safely achieve its next target, the unglamorously named 2014 MU69, which it is hoped will reveal more about mid-sized KBOs and their role as building blocks of the solar system, when the probe reaches it in 2019.
Friday 13th: WTF Struck Earth’s Atmosphere
Friday 13th is said to be unlucky for some. Friday 13th November 2015 certainly proved to be unlucky for one object, which slammed into the Earth’s atmosphere high over the Indian Ocean close to the beautiful island of Sri Lanka, to burn up during a fiery descent from orbit.
Such collisions are not rare – there are some 500,000 pieces of so-called “space junk” orbiting the Earth which are being tracked, all of which are of varying sizes and which tend to eventually either strike the denser parts of Earth’s atmosphere or get slowly dragged back down as a result of tiny amounts of friction generated over the years / decades by their passage through the very, very tenuous outer reaches of Earth’s atmosphere. What made this particular piece so interesting was that it could be closely tracked, and no-one actually knew precisely what it was.
Officially designated WT1190F, the object was inevitably dubbed “WTF”, a reflection of the initials in its name and the fact no-one could positively identify it. Closest speculation is that give the eccentric nature of its orbit, which has seen it swing very close to Earth before passing well beyond the Moon before swinging back once more, is that it is a remnant or debris from a lunar mission – perhaps one of the Apollo flights.
Whatever its origins, the object re-entered the atmosphere around midday local time in Sri Lanka (about 06:19 GMT / 01:19. EST). On hand to see it was worldwide collaboration of researchers who observed its passage from a jet aircraft, capturing video and other data of the object’s final moments.
Approximately one metre (3 ft) across, the object hit the Earth’s atmosphere at around 39,600 kph (24,600 mph), its velocity giving rise to its bright glow despite its small size; at that speed, every kilogramme (2.2 lbs) of material has about the same amount of energy as 10 kilograms (22 lbs) of high explosives.
It’s hoped that the data gathered about the event will reveal more about WT1190F’s identity and provide more information to help refine debris tracking and re-entry models to help with tracking and monitoring some of the 21,000 pieces of space junk thought to be larger than 10cm (4 in) in size and smaller near Earth objects (NEOs) which may also at some point collide with the Earth’s atmosphere.