Saturn’s giant moon, Titan, has been a source of speculation of decades. Shrouded in a dense, methane-nitrogen rich atmosphere, potentially harbouring a liquid water ocean beneath its crust, the moon has long be thought to have the conditions in which basic life might arise.
The joint NASA-ESA Cassini-Huygens mission has, over the span of thirteen years, added immeasurably to our understanding of Titan – and to the mysteries of its potential. In doing so, it has also provided us with evidence of processes taking place which are the precursors to the development of life. For example, we know that within Titan’s ionosphere, nitrogen, carbon and hydrogen are exposed to sunlight and energetic particles from Saturn’s magnetosphere. This exposure drives a process wherein these elements are transformed into more complex prebiotic compounds, which then drift down towards the lower atmosphere and form a thick haze of organic aerosols that are thought to eventually reach the surface.
However, while the drivers of the process are known, the nature of the process itself has been something of a mystery – one which an international team of scientists led by the University College London (UCL) think they now understand. In Carbon Chain Anions and the Growth of Complex Organic Molecules in Titan’s Ionosphere the team identify Titan’s upper atmosphere contains a negatively charged species of linear molecule in Titan’s atmosphere called “carbon chain anions” – which, it has in the past been theorised, may have acted as the basis for the earliest forms of life on Earth.
The molecules were detected by CAPS, the Cassini Plasma Spectrometer, as the vehicle passed through the upper reaches of Titan’s atmosphere on a final flyby before commencing its “Grand Finale” of flights between Saturn and its rings. The discovery came as a surprise, as carbon chain anions are highly reactive, and should not survive long in Titan’s atmosphere. However, what particularly caught the attention of the science team was that the data show that the carbon chains become depleted closer to the moon, while precursors to larger aerosol molecules undergo rapid growth. This suggests a close relationship between the two, with the carbon chains ‘seeding’ the larger molecules – those prebiotics mentioned above – which then fall to the surface.
“We have made the first unambiguous identification of carbon chain anions in a planet-like atmosphere, which we believe are a vital stepping-stone in the production line of growing bigger, and more complex organic molecules, such as the moon’s large haze particles,” said Ravi Desai, the lead author for the study in a press release from UCL.
He continued, “This is a known process in the interstellar medium – the large molecular clouds from which stars themselves form – but now we’ve seen it in a completely different environment, meaning it could represent a universal process for producing complex organic molecules. The question is, could it also be happening at other nitrogen-methane atmospheres like at Pluto or Triton, or at exoplanets with similar properties?”
With its rich mix of complex chemistry coupled with its basic composition, Titan is something of a planetary laboratory; one which probably mirrors the very early atmosphere surrounding Earth before the emergence of oxygen-producing micro-organisms which started the transformation of our atmosphere into something far more amenable for the advance of life. As such, the discovery of carbon chain anions in Titan’s atmosphere potentially confirms that long-held theory that they help kick-start the life creating processes here on Earth, and suggest conditions on Titan might allow the same to happen there. It also offers insight into how life might start elsewhere in the galaxy.
“These inspiring results from Cassini show the importance of tracing the journey from small to large chemical species in order to understand how complex organic molecules are produced in an early Earth-like atmosphere,” Dr Nicolas Altobelli, ESA’s Cassini project scientist, said in the same press release. “While we haven’t detected life itself, finding complex organics not just at Titan, but also in comets and throughout the interstellar medium, we are certainly coming close to finding its precursors.”
Dream Chaser ISS Flights target 2020 Commencement
Sierra Nevada Corporation (SNC) has confirmed than United Launch Alliance (ULA) will provide the veritable Atlas V booster as the launch vehicle for the Dream Chaser Cargo mini-shuttle, which will be joining fleet of uncrewed vehicles from America, Russia and Japan keeping the International Space Station (ISS) supplied with consumables, equipment and science experiments. The company also indicate that launches of the vehicle could start in 2020.
Dream Chaser was originally conceived to fly crews to and from the ISS as part of NASA’s commercial crew transportation joint venture with the private sector. Four companies vied for contracts to supply NASA with vehicles capable of shuttling up to six personnel to and from the space station. Despite being one of the most advanced of the designs in terms of feasibility and development, the Dream Chaser was not selected for that work, with NASA opting for the SpaceX Dragon 2 vehicle and Boeing’s CST-100 Starliner capsule.
However, support within the US space agency for the Dream Chaser continued, allowing SNC to propose the development of Dream Chaser Cargo, a revised version of the original concept, capable of supplying up to 5.5 tonnes of cargo to the ISS. In January 2016, in renewing its contract with SpaceX (Dragon) and Orbital ATK (Cygnus) for such resupply missions, NASA extended it to include SNC. This was followed a year ago by formal approval being given for Dream Chaser missions to the ISS, which allowed SNC to push ahead with testing of the revised vehicle.
Dream Chaser will launch atop the commercial Atlas V in its most powerful configuration, dubbed Atlas V 552, with five strap on solid rocket motors and a dual engine Centaur upper stage. The cargo vehicle will be held inside a five metre diameter payload fairing with its wings folded. Cargo will be carried both within the vehicle itself and in a support module mounted on the rear of the spacecraft, which will also house a docking adaptor for connecting with the space station. The latter will be supplied to SNC by the European Space Agency, which is also supplying NASA with the Service Module for the Orion multi-Purpose Crew Vehicle.
In addition to flying up to 5.5 tonnes to the ISS, Dream Chaser Cargo will be able to return some 2 tonnes of equipment, experiments and other items from the space station to Earth, where it will make a conventional runway landing using the former space shuttle runway at Kennedy Space Centre – or any other suitable landing facility in the United States.
It is expected that Dream Chaser cargo will fly a total of six missions to the ISS between 2020 and 2024, when it is currently anticipated the space station will be decommissioned.
Did Martian Volcanoes Harbour Life?
In the see-sawing of opinion on whether Mars was – or might be – the abode of basic life, which recently tipped toward Mars currently being hostile towards simple micro-organisms, a new study suggests that much friendlier conditions might have existed in the past, and in something of an interesting location: around ancient volcanoes lying along the Vallis Marineris, the “Grand Canyon” of Mars.
Some 4,000 kilometres in length (that’s stretching coast-to-coast across America) or roughly one fifth of the circumference of Mars, Vallis Marineris can be up to 100 kilometres (60 miles) across and 7 to 10 kilometres deep. Formed in the early period of Martian history – around the same time as the massive Tharsis Volcanoes, and the huge Hellas basin on the far side of Mars relative to the Tharsis Bulge (the formation of all three may well be connected) – this huge scar on Mars is a unique location. It is so deep, that the atmosphere along its floor has a higher average density than the atmosphere across the rest of the planet’s surface. It has its own system of clouds, fog and mist, noticeably during the morning periods, and it is the home of a wide range of geologic features.
One of the latter takes the form chains of volcanoes and solidified lava flows which can be found throughout the length of Vallis Marineris and which can be quite numerous. Coprates Chasma, one of the deepest points in the network, for example, is home to over 130 such volcanoes and lava flows. These are particularly interesting because they date from much later in Mars’ history than the planet’s primary period of volcanic activity.
The latter was thought to take place in the planet’s Noachian to Late Hesperian periods – around 3.7 to 3 billion years ago, and gave rise to the massive Tharsis volcanoes: Arsia Mons, Pavonis Mons, and Ascraeus Mons, as well as mighty Olympus Mons and other major regions of volcanic activity on the planet – and to Vallis Marineris itself. Instead, the volcanoes along the floor of the valley’s chasms appear to be as little as 300-400 million years old, placing them in the planet’s Amazonian Period, which extends from around 3 billion years ago to the present day, and is likely the period in which liquid water was still in evidence on the surface of Mars.
Now, a new study, Amazonian Volcanism Inside Valles Marineris on Mars, which uses data gathered from the Compact Reconnaissance Imaging Spectrometer (CRISM) aboard NASA’s Mars Reconnaissance Orbiter, reveals that the mineral composition of the volcanic cones and ancient lava flows within Coprates Chasma has a high silica content, including opaline-like substances. The latter are water-bearing materials often produced by hydrothermal processes – where silicate structures form from supersaturated, hot solutions of minerals that cool to become solid.
On Earth, micro-organisms are often found within opal deposits since they form in energy and mineral-rich environments, where microbial lifeforms thrive. The presence of these minerals in the Coprates Chasma region could therefore mean that ancient micro-organisms once thrived there. Moreover, such organisms could also be fossilized within the mineral-rich lava rock, making it a tempting target for future research – although reaching the floor of any part of this canyon system will be a challenge in itself.
SpaceX Confirm November for Falcon Heavy Launch
After indicating the its maiden flight is unlikely to be successful due to significant vibration issues (see here for more), Elon Musk has confirmed that November is the planned month for this first flight of the new Falcon Heavy launch system, although an actual date has yet to be given.
The announcement came via Twitter, and the launch will take place at Kennedy Space Centre’s Pad 39A, which SpaceX took over from NASA specifically to cater for Falcon Heavy launches (and potentially for their upcoming super rocket).
The Falcon Heavy is based on SpaceX’s Falcon 9 rocket and uses two Falcon 9 first stages strapped to a central core (itself a modified Falcon 9 booster). Like the Falcon 9, which can launch into orbit and land its first stage back on Earth for later flights, the Falcon Heavy is designed to be reusable. In fact, the maiden flight will use two previously flown Falcon 9 first stages as its boosters.
Once the vibration issue is solved – and SpaceX is confident of doing so – the Falcon Heavy will, for a time, be the most powerful rocket in operation, capable of lifting 54 tonnes to low Earth orbit, 22 tonnes to geostationary transfer orbit and around 10 tonnes to Mars. However, when it enters service, NASA’s Space Launch System will initially be able to hoist 70 tonnes to low Earth orbit (Block 1 vehicle) then 97.5 tonnes (Block 1b vehicle), and a massive 123 tonnes (Block 2 vehicle).
Musk has thrown open an invitation for people to travel to Kennedy Space Centre to see the Falcon Heavy, once the date is confirmed, noting that it will be an exciting view. He also added that, given there is likely to be a vibration issue, he hopes the vehicle will be well clear of the launch pad should problems occur, to reduce the risk of pad damage should the worse happen.
Has The First Exomoon Been Detected?
I’ve covered a lot of the news about exoplanets in these weekly updates – planets orbiting other stars. Now comes word that the first exomoon – a natural satellite orbiting a planet parented by another star – has been found.
While the catalogue of explanets is growing, largely thanks to the work of the Kepler Space Observatory, discovering moons orbiting them is quite a different matter. Nevertheless, A team led by David Kipping of Columbia University, believe they have done just that – and by using the same technique used to initially identify what might be planets orbiting a distant star: the dimming that occurs in the brightness of the star as the planet passing between it and the point of observation.
Kipping’s team observed a planet orbiting Kepler-1625, a start around 4,000 light years away, and have reported that they recorded three dips in the planet’s reflected light as it made three trips around its star. While the place a high level of confidence that the data indicates a moon to be responsible, the team also acknowledge that other factors may have caused the apparent dips.
For a start, at 4,000 light years, the light the planet is reflecting from its parent star is exceptionally dim, so the “dips” could simply be errors in the data the team has gathered, rather than an actual effect. As such, they’ve offered their finding to the larger astronomical community to either confirm or quash – such as via data gathered by the Hubble Space Telescope (HST).
However, if the planet – which is larger than Jupiter and orbits its parent star every 287.3 Earth days – does have a moon orbiting it, the moon itself would likely have to be around the size of Neptune, making it the largest moon yet discovered.
Inara Pey: Living in a Modemworld 