The night of Sunday 27th / Monday 28th September promises a very special astronomical event for those fortunate enough to have clear skies overhead and are willing to stay up late (in the UK and Europe). It will see a total lunar eclipse take place at the time when the Moon reaches perigee, its closest approach to Earth in its orbit and giving rise to both a so-called “supermoon” and a “Blood Moon”.
A “supermoon” occurs when a full moon coincides with the time when the Moon is nearing its minimum distance to Earth, a distance of roughly 363,000 kilometres (226,875 miles), leading to it appearing 7-8% larger than when seen as a full Moon at other points in its orbit. A “blood moon” is the result of the Earth’s atmosphere, lying between the Sun and Moon, scatter blue light more strongly than red, so the latter reaches the Moon more strongly, giving it a reddish-brown colour when seen from Earth.
Lunar eclipses are not that rare – this one will be the second of 2015, for example. However, “supermoons” are somewhat rarer. The last was in 1982, and the next will not be until 2033. So, if you want to see a really big blood moon, and you live in Western Europe, West Africa, the Eastern side of the USA and Canada or south America, then the 27th / 28th September is the night to do so. People further afield – eastern Asia, the middle east, eastern Europe and the western sides of Canada, the USA and South America will see a partial eclipse.
In the UK, the period of eclipse will start at around 01:00 BST (00:00 GMT) on the morning of Monday, 28th September, and run through until around 05:00 BST (04:00 GMT). That’s from 20:00 through to around 01:00 EDT in the USA / Canada, and 02:00 through 06:00 CET in Europe).
The eclipse brings to a close what is referred to as a “tetrad” of total lunar eclipses – that is, four occurring “back-to-back”, with no partial eclipses between them, the first of which occurred in April 2014 and the “middle two” in October 2014 and April 2015. Some have a misguided view that this “tetrad” as being of particular significance because such events are “rare”, and this particular one started on the Passover.
However, while there can be long periods of time between occurrences of tetrads, they can also pop-up relatively frequently. For example, this century will see a total of nine tetrads occur, the first having taken place in 2003/4. Nor is the fact that this particular series started on the Passover particularly unusual; there have been eight tetrads so far coinciding with Passover since the first century AD.
So, if you are in a position to see the eclipse, you can leave the tinfoil hat on the table and step outside quite safely. Totality should occur around two hours after the eclipse starts (e.g. 03:00 BST in the UK / 04:00 CET, 22:00 EDT on the 27th September), and that’s the best time to enjoy the blood moon in all its glory.
The eclipse will also give NASA the chance to measure the full range of temperature variations during such an event. This will be done by the Lunar Reconnaissance Orbiter (LRO), a solar-power vehicle which has been observing the Moon since 2009.
Normally during an eclipse, the LRO has most of its systems powered down to reduce the load placed on the battery systems. However, mission controllers are confident they will be able to run an instrument which will allow it to accurately measure the amount of heat loss the surface of the Moon experiences when inside the Earth’s shadow, further helping them to understand the composition of the Moon’s regolith and its function as an insulator.
NASA Announces … A “Major” Mars Mystery Announcement
NASA and Nature Geoscience have had science blogs and news sources agog since Friday, September 25th, after they made a joint announcement that they would be announcing a “major science finding” about Mars on Monday, September 28th, which resolves a “mystery” about the Red Planet.
Such pre-announcements isn’t that unusual; nor is that fact that the information is supplied ahead of time to certain media outlets, albeit under embargoed. However, as might be expected, it has led to considerable speculation as to what NASA might be announcing – including some speculation they’ll be announcing “life on Mars”.
To be honest, this latter point is highly unlikely. Even Curiosity, NASA most advanced vehicle on the surface of Mars isn’t actually equipped to directly identify microbial life on Mars – it can only determine whether conditions around it may once have been suitable for live to have possibly have started.
What seems more likely, is that NASA will be discussing further studies into the potential for water flowing on the surface of Mars in current times. This would particularly given that one of those addressing the press on Monday will be Lujendra Ojha.
In 2011, whilst still an undergraduate, Ojha published the first in a series of papers on seasonal water flows on Mars following studies of what are called recurring slope lineae (RSL) features. These are ridges and rilles which appear on the slopes of hills and craters, and the edges of canyons, which appear to be seasonal in nature and which, on Earth, are associated with water flows.
The RSL features on Mars are particularly common in equatorial regions, seem to be most noticeable in the spring season, then gradually fade during the year, before being somehow renewed again.
So far, the mechanism which causes these linear features is unknown, but the thinking is that there is some mechanism as work which is bringing sufficient water to the surface of Mars to cause outflows of sufficient water to avoid immediate sublimation as it holds dust and dirt in suspension. However, as Ojha himself has noted, until now, the mechanisms which cause these RSL features – and whether they involve water – have remained unclear. Thus, the common thinking is that the NASA announcement will be to announce they now understand the mechanism(s) which are at work, and they may well involve water, and possibly some complex atmospheric processes.
I’ll have more on this in the next Space Sunday update.
Pluto Friday on the 28th September, revealed more stunning pictures of the solar system’s most well-known dwarf planet, including the stunning colour image shown above, which reveals the rich and subtle colours presents on the surface of Pluto, and well as some of its many surface features.
Another of the most eye-catching is that of the region informally dubbed Tartarus Dorsa, a strange landscape of linear ridges which almost look like a snake’s skin, which appeared close to the planet’s day / night terminator at the time the New Horizons spacecraft performed its close flyby of Pluto.
“It’s a unique and perplexing landscape stretching over hundreds of miles,” said William McKinnon of the New Horizons Geology, Geophysics and Imaging (GGI) team. “It looks more like tree bark or dragon scales than geology. This’ll really take time to figure out; maybe it’s some combination of internal tectonic forces and ice sublimation driven by Pluto’s faint sunlight.”
New, very high-resolution images from the LORRI camera have also revealed the icy plain informally named Sputnik Planum also has a fairly complex form. Far from being a relatively smooth ice surface, the images show the plain to be pockmarked with small rounded depressions and rough-edged ridges.
Several theories for these features have been put forward, including the idea that the formations might actually be the result of surface material being blown into snowy dunes. Another suggests that the pockmarks might be the result of very localised sublimation giving rise to the pockmarks.
Further data returned from New Horizons has revealed more about Pluto’s methane, which has a complex distribution across the planet. The Sputnik Planum, for example shows high concentrations of the gas, while the mountain regions around it and the neighbouring dark region dubbed Cthulhu Regio show almost no methane at all. High concentrations of methane has been mapped along other plains and around crater rims, but almost none appears to be present in the craters themselves.
“It’s like the classic chicken-or-egg problem,” said Will Grundy, New Horizons surface composition team lead. “We’re unsure why this is so, but the cool thing is that New Horizons has the ability to make exquisite compositional maps across the surface of Pluto, and that’ll be crucial to resolving how enigmatic Pluto works.”
Dawn, the NASA / ESA joint mission to explore two of the solar system’s three “protoplanets” located in the asteroid belt between the orbits of Mars and Jupiter, has returned some of the best images yet of Ceres, including the mysterious bright spots in Occator crater.
The new image mosaic, taken from an orbit just 1,470 km (915 mi) above Ceres, has a resolution of 140m (450 ft) per pixel and reveals considerable detail about the crater. It is hoped that additional data returned with the images will reveal more about the composition of the bright spots, which have previously been linked to a possible highly localised atmosphere within the crater.
“Dawn has transformed what was so recently a few bright dots into a complex and beautiful, gleaming landscape,” said Marc Rayman, Dawn’s chief engineer and mission director. “Soon, the scientific analysis will reveal the geological and chemical nature of this mysterious and mesmerizing extraterrestrial scenery.”
The spacecraft is now engaged in the third of six mapping orbits – each of which takes 11 days to complete – of Ceres. Once these have been completed in October, the spacecraft will manoeuvre down to its lowest orbit, just 375 km (230 mi) above Ceres.