by Duncan Lunan

Moon

The Moon is New on September 3^rd, Full on September 18^th, a ‘Supermoon’, Full at its closest to Earth.  The very young crescent Moon is close to Venus on September 5^th.   On the morning of the 18^th between 3.12 and 4.15 a.m., the Moon is partially eclipsed, visible from Europe, Africa and the Americas, but only by 8% at most.   On the 23^rd the Moon is above Jupiter, a day after the Autumn Equinox.

Mercury

The planet Mercury is low in the morning sky in the east in the first half of September, below the Moon on the 1^st, furthest from the Sun on the 5^th, disappearing by the middle of the month.

Venus

Venus is in the evening sky, moving from Virgo into Libra, passed by the Moon on the 5^th, but still low in the twilight, setting about 8 p.m..  As always, take great care if searching for it before sunset.

Earth

The Earth was subject to two periods of glaciation between 750 and 630 million years ago, generally referred to as ‘Snowball Earth’  (Fig. 1), eventually ended by global warming due to volcanic activity. 

Since the idea was first proposed there has been a lot of argument about whether the planet was completely frozen, or had ‘oases’ of open water  (Fig. 2), or a strip around the equator remained clear (Fig. 3), allowing the survival of marine life, since the continents were still sterile. 

That was the situation after a cosmic collision in Sydney Jordan’s Lance McLane strip  (Fig. 4), which ran in the Daily Record 1976-1988 before being syndicated overseas as an alternative version of his longer-running Jeff Hawke. 

Some evidence of wave action has been found on beaches which were near the equator during Snowball periods.  But now, in the Garvellachs of the Inner Hebrides, “New research, led by UCL (University College London), found that the Port Askaig Formation, composed of layers of rock up to 1.1 km thick, was likely laid down between 662 to 720 million years ago during the Stuartian glaciation – the first of two global freezes thought to have triggered the development of complex, multicellular life.”  (‘Scottish & Irish Rocks Key to Discovering the Triggering of Snowball Earth’, Orkney News, August 23^rd 2024).  The implication is that the ice was universal during that period, but ongoing study will doubtless give us the answer.

Just before I wrapped up this column comes sad news for Earth-Space science:  Salsa, the first of the ESA Cluster satellites to run out of fuel, is to be deorbited on or about September 8^th  (Figs. 5 & 6).  Back in the early 1990s, ESA’s big solar project was the synchronised launches of SOHO, to the Earth-Sun L1 point a million miles sunward  (Fig. 7), and two pairs of Cluster satellites into 54-hour Earth orbits ranging up to 117,000 km, three times the height of communications satellites  (Fig. 8).  SOHO was launched successfully in 1995, recovered in 1998 after a near-fatal loss of control systems, and continues to make headlines – it’s expected to return spectacular pictures of Comet Tsuchinshan-ATLAS as it passes through the view field of SOHO’s LASCO C3 camera between October 7^th and 10^th   (Fig. 9).  The comet is closest to the Sun on September 27^th and closest to Earth on October 12^th, but may not surpass binocular visibility.

The first Cluster satellites, however, were written off when the first Ariane V exploded during launch in 1996, due to erroneous use of Ariane IV software for part of the trajectory  (Figs. 10 & 11). 

The satellites were rebuilt  (Figs. 12 & 13)  and launched on Russian rockets in 2000  (Fig.  14), since when they have achieved a long run of success  (e.g. Figs. 15 & 16), despite a software glitch and emergency recovery in 2010. 

Of the remaining three satellites, Rumba will re-enter in November 2025, followed by Tango and Samba in August 2026, all into the ‘Pont Nemo’ disposal area which was used by the Mir space station and others  (Fig. 17), controlled by ESA tracking stations in South America  (Fig. 18).  (David Dickinson, ‘ESA Cluster Satellite to Re-enter in Early September’, Universe Today, August 30^th 2024.) 

Successor missions are in preparation, with SMILE (Solar wind Magnetosphere Ionosphere Link Explorer)  launching in late 2025, and Proba-3, continuing another successful series, for launch next month, both going into similar far-ranging orbit around the Earth.  Proba-3 will feature a free-flying, solar eclipsing disk, which is a technique which shows promise in the search for earthlike exoplanets. 

Mars

Mars rises at about 11.30 p.m, passing from Taurus into Gemini, and growing brighter before its closest approach in January – Mars and Jupiter have been making a spectacular pair during August, on the occasional clear nights that we get on Arran.  Mars is below the Open Cluster M35 on the night of September 8-9^th, and near the Moon on the 25^th.

Leaving its river valley exploration for now, the Perseverance rover is making for the rim of Jezero crater, whose floor it has already explored.  The climb will take several months, including risky 23 degree slopes, and take the rover to 1000 feet above the crater floor and the gap in the rim where the river flowed into it  (Fig. 19).  The hope is that on the rim there will be rocks from deep below the Martian crust and still earlier in the planet’s history.

NASA’s next Mars mission consists of two identical ESCAPADE (Escape and Plasma Acceleration and Dynamics Explorers)  probes, Blue & Gold, which are scheduled for launch on October 13^th.  This one is taking another big chance because it will be the maiden flight of the New Glenn booster, developed by Jeff Bezos’s Blue Origin company.  The BE-4 methane-powered first stage engine performed successfully on the United Launch Alliance’s Vulcan rocket in January;  the Peregrine lunar probe subsequently had a crippling fuel leak, but that was after separation from the booster.  But both the second and third test vehicles have encountered major setbacks, with a second stage explosion of # 2 during a test fire, and the collapse of # 3 when engineers tried to move it without pressurising the tanks, so it remains to be seen whether the Mars launch will happen.  If the launch window is missed, there isn’t another till 2026.

Meanwhile, continuing study of the seismic results from the Insight Mars lander has produced a spectacular result.  Insight ceased transmission in 2022 due to the buildup of dust on its solar panels, but before that it detected a large meteorite impact in March 2022 and an even larger Marsquake in May that year. 

Ongoing analysis has revealed what appears to be unequivocal evidence of liquid water, seven to 13 miles below the landing site  (Fig. 20), and suggesting that there may be many more such lakes deep in the Martian crust or at the boundary with the mantle, enough to cover the entire planet to a depth of one mile  (after smoothing it out, presumably, because the northern hemisphere is lower than the south and was once a sea).  Obvious question are, are there underground heat sources, and has any primordial life survived in the depths – at which the water is likely to be beyond the reach of Elon Musk’s intended Mars colonists.  That in turns raises the question, is there liquid water nearer the surface?  During the Viking Orbiter missions in the 1970s it was suggested that there might be, escaping into the atmosphere at Lacus Solis, which Percival Lowell had suggested was the capital of Martian civilisation.  There’s ongoing argument about whether there are seasonal outbreaks into craters from their rims  (which might make the Perseverance results interesting), and about whether the deep penetrating radar of ESA’s Mars Express has found water below the south polar cap, or merely ice.  Ice has been found in quantity below the surface at the equator… 

In the same August 24^th issue of the online journal EarthSky  (highly recommended), it seems that the argument about whether an asteroid or a comet killed the dinosaurs has finally been settled.  It seems strange now to think back to the 1960s, when it was generally assumed that the Earth’s atmosphere protected us from impacts, and scientists who thought otherwise had to publish in the regular science feature of Analog Science Fiction/Science Fact.  They had examples to point to like the Barringer and Chubb craters in North America, and the Vredevoort Ring in South Africa, but those were taken to be rare exceptions to the rule.  A much-repeated objection was that there was no crater to explain the dinosaur extinction – in reading NASA technical translations of Soviet scientific literature I learned that they’d found a crater of suitable size below Antarctica, but I’ve never heard any more about that.  It was a big sensation when the BBC’s The World at One announced in 1979 that one had been found, centred off the coast of Yucatan, and powdered rock from it had been found all over the world at the Cretaceous-Tertiary boundary marking the extinction.  Subsequently the layer was found to be enriched with iridium, from an asteroid or comet, and contained soot from global wildfires caused by ejecta of molten rock.  I remember David Attenborough making a big deal of that in a programme on the survival of birds and reptiles.

But was the impactor an asteroid, about seven miles across, or a less dense comet about ten miles across, to produce similar effects?  After 45 years of debate, it’s been found that the K-T boundary layer is also enriched with ruthenium, osmium, rhodium, platinum and palladium, in quantities consistent with its having been a C-type carbonaceous asteroid, of types found in the Outer Belt, ranging beyond the orbit of Jupiter  (Fig. 21).  (Paul Scott Anderson, ‘Dinosaur-Killing Asteroid Came from Beyond the Orbit of Jupiter’, EarthSky, online, 22^nd August 2024, reprinted 24^th August.)  The ratios are not consistent with other asteroid types, nor with terrestrial volcanic activity, although there was a lot of that in the Deccan Traps at the time.  The good news is that nothing that size is due to hit the Earth within the next 100 years.  Less good news is that there’s currently no technology capable of dealing with one – in my Incoming Asteroid!  What Could We Do About It? the discussion group’s ‘designer hazard’, which could be dealt with, was only 1 kilometre across.

Jupiter

Jupiter in Taurus rises at 10.30 p.m., and is passed by the Moon on the 23^rd, as above.  ESA’s JUpiter Icy Moons Explorer  (JUICE)  made a double gravitational slingshot of the Earth and Moon on 19^th and 20^th August  (Figs. 22 & 23), the first time that has actually been done, though the idea goes back a long way. 

In the Jeff Hawke story ‘The Search for Asteron’  (Daily Express 23/6/55 – 1/11/55), the asteroid-bound spaceship Argosy made course corrections by lunar slingshot both on departure and return  (Figs. 24 & 25), and the Lucy mission now on the way to the Trojan asteroids has made a similar Earth flyby, though passing the Moon at greater distance. 

JUICE has a Venus flyby and two more Earth passes to make before finally departing for Jupiter  (Fig. 26), but everything’s looking good so far. 

Saturn

Saturn in Aquarius is at opposition on September 8^th, due south at midnight GMT  (1 a.m. BST), moving westwards against the stars as the Earth overtakes it.  The Moon passes Saturn on September 17^th.  During opposition, Saturn’s large moon Titan will no longer pass above or below Saturn as it did last month, but the rings will temporarily become more visible before closing up for Saturn’s equinox in March 2025  (Fig. 27). 

Uranus

Uranus in Taurus rises at 9 p.m., at its stationary point on September 1^st and beginning to move westwards on the 14^th, near the Moon on the 22^nd.

Neptune

Neptune in Pisces is also at opposition, on September 21^st, rising about 9.30 p.m., and is close above the Moon on the 18^th, as above.

Incoming Asteroid!  What Could We Do About It? and Duncan Lunan’s other recent books are available through Amazon – for details see Duncan’s website, http://www.duncanlunan.com.

You can download a copy of the Sky Map for September here: