This summary is published every Monday, and is a list of SL viewer / client releases (official and TPV) made during the previous week. When reading it, please note:
It is based on my Current Viewer Releases Page, a list of all Second Life viewers and clients that are in popular use (and of which I am aware), and which are recognised as adhering to the TPV Policy. This page includes comprehensive links to download pages, blog notes, release notes, etc., as well as links to any / all reviews of specific viewers / clients made within this blog
By its nature, this summary presented here will always be in arrears, please refer to the Current Viewer Release Page for more up-to-date information.
July 4th is a special date in American history, and this year it will, for space exploration enthusiasts be doubly meaningful, as it will mark the point at which we have been examining and exploring Mars continuously for 20 years without a single break.
Of course, attempts to explore and understand Mars began much earlier than that. We first started launching missions to the Red Planet far back in the 1960s. The first successful mission – the United States’ Mariner 4 probe – shot past Mars in July 1965, returning just 22 fuzzy images as it did so, travelling too fast and without any fuel to achieve orbit. In 1969, and total overshadowed by the Apollo 11 mission to the Moon, Mariner 6 also flew by Mars in July, and was followed in August by its twin, Mariner 7, becoming the first dual mission to visit another world in the solar system.
The first American mission to orbit Mars was Mariner 9, which arrived in orbit in November 1971, the exact time Mars was wreathed in a series of globe-spanning dust storms. Fortunately, the space vehicle had a planned orbital life of around 18 months, and successfully waited out the storms before returning the most spectacular images of Mars yet seen – including the mighty Tharsis volcanoes and the great gash of the Vallis Marineris, named in honour of the probe.
Russia also finally successfully reach Mars orbit in 1971 with the dual Mars 2 and Mars 3 missions. The former arrived just days after Mariner 9, and the latter became the first mission to successfully deploy a lander to the surface of Mars – although the craft ceased transmitting just 15 seconds after a safe landing had been confirmed, probably due to the dust storms. Unlike Mariner 9, the Russian orbiters had a shorter operational lifespan, and both ceased operations before the dust had fully cleared, resulting in them being classified as “partially successful” missions.
Then, in 1976 came the twin Viking Missions, comprising two pairs of orbiter and lander vehicles. Even now it remains one of the most ambitious robotic missions ever undertaken. The Viking 1 orbiter and lander combination launched on August 20th, 1975 and arrived in Mars orbit on June 19th, 1976. Viking 2 departed Earth on September 9th, 1975 and arrived in Mars orbit on August 7th, 1976.
Viking Lander 1 had been scheduled to depart its orbiter and attempt a landing on Mars on July 4th, 1976 – the 200th anniversary of America’s independence. However, images of the landing site taken by the orbiter revealed it to be far rougher terrain than had been thought, so the landing was delayed while an alternative site was surveyed. The lander eventually touched-down on July 20th, 1976, marking the seventh anniversary of the first mission to land on the surface of the Moon. Viking lander 2 touched down half a world away on September 3rd, 1976.
Viking really was a landmark – and controversial – mission. Landmark, because they utterly changed our understand over Mars during years both orbiters and landers operated. Controversial because it is still argued to this day by some that two of the five life-seeking experiments carried by each of the landers did find evidence of Martian microbes living in the planet’s regolith, although it seems more likely that the positive results – in both cases, from the same two experiments – were the result of inorganic chemical reactions between mineral in the Martian soil samples and elements within the experiments.
After Viking the came a pause. While missions continued to be launched to Mars by the USA and Russia in the 1980s and early 1990s, none of them were successful. It was not until 1997 that the current trend of having vehicles continuously operating around and on Mars began – and which NASA has been celebrating, having been the stalwart of the 20-year effort of these 24/7 operations.
This run technically started in early November 1996, with the launch of NASA’s Mars Global Surveyor (MGS) mission. It was followed a month later by the NASA Pathfinder Mission. By a quirk of orbital mechanics, the Pathfinder Mission – designed to test the feasibility of placing a lander and small rover on Mars – arrived at Mars first, performing a successful aerobraking and landing on July 4th, 1996.
The Pathfinder lander arrived in Ares Vallis on Mars, an ancient flood plain in the northern hemisphere in an innovative way. A conventional aerodynamic heat shield protected the craft through initial entry into, and deceleration through, the upper reaches of Mars’ tenuous atmosphere. Having slowed from a velocity of several thousand kilometres an hour to just over 1300 km/h, allowing a supersonic parachute to be deployed. This slowed the vehicle’s descent to around 256 km/h and lowering the vehicle to just 355 metres above the surface of Mars, where several things happened.
Firstly, a tetrahedron cocoon of protective airbags was inflated all around the vehicle in less than a second. A set of rocket motors in the back shell beneath which the airbags and lander were suspended, then fired. These slowed the vehicle almost to a hover about 15-20 metres above the ground, at which point the tether connecting the cocooned lander was cut, and the lander fell to the ground, bouncing several times before coming to rest and the airbags were deflated and drawn back underneath the lander. The triangular lander was designed to right itself while unfolding its three solar power “petals”, however, this was not required as the lander came to a stop the right way up, allowing the petals to be deployed, and – after check-out tests – the little Sojourner rover was command to drive down off of the lander and onto the surface of Mars. The same system would later be used for the MER rover missions.
As a proof of concept mission, Pathfinder was not intended to be a long duration mission. Just 65 cm (25.6 in) long and 48 cm (19 in) wide, the 10.5 kg (23 lb) Sojourner rover had a top speed of 1 cm a second, so it could never roam far from its base station; in fact it never went further than about 12 metres (39 ft) from the base station, which acted as a communications relay as well as studying the Martian atmosphere and imaging Sojourner in action. Nevertheless, the mission exceeded expectations, lasting some 3 months, with the little rover examining 16 points of interest with its humble 0.3 megapixel cameras and its on-board spectrometer.