The Sky Above You – October 2023

By Duncan Lunan

The Moon will be New on October 14th, and Full on October 28th. On the night of 28th October there’s a partial lunar eclipse between 8.35 p.m. and 9.53 p.m., visible from the UK, Europe, Africa and Asia. British Summer Time ends the following night, the 29th.

Since the last ‘The Sky Above You’ Japan’s SLIM, Smart Lander for Investigating Moon, has been successfully launched on September 6th, and on September 14th it was announced that the first critical operation period had been completed successfully, with solar panels, communications, propulsion and other systems working well.  The spacecraft is in a 20-day checkout period, in an orbit taking it beyond the distance of the Moon, from which it will make a low-velocity transfer into lunar orbit, in several months’ time, before attempting a landing.

There may be less good news from NASA’s Shadowcam satellite, which has been orbiting the lunar poles since December 2022.  While there is ice in Permanently Shadowed Regions at the lunar poles, it appears that they came into being only c.3.4 billion years ago, gradually expanding since as the Moon moved away from the Earth.  The earliest definite detection of water on the Moon came in 2009 with the impact of the L-Cross probe in Cabeus crater.  Patrick Moore said he would eat his hat on Selsey beach, live on The Sky at Night, if any was found, but somehow he didn’t get round to doing it.  It now appears that Cabeus became Permanently Shadowed only about 1 billion years ago.  Remarkably enough, there may be more of the water ice at Mercury poles, predicted by the Arran astronomer V.A. Firsoff in 1962, because those crater floors are older and more extensive.  (Paul Scott Anderson, ‘There May Be Less Water Ice on the Moon than we Thought’, EarthSky, September 21st, 2023).  However, that headline assumes an even rate of deposition, over billions of years, which may be far from the case.  The first Permanently Shadowed Regions evidently formed during a period of intense volcanic activity, when the big impact basins were filling with lava, and it’s now thought that large amounts of water were released then from inside the Moon.  Comet impacts could also change the position drastically.  It’s been calculated that a single comet the size of Hale-Bopp, in 1987, could in theory deposit enough water to make the entire Moon habitable.

The planet Mercury is in the morning sky in early October, but very low and soon disappearing into twilight, at superior conjunction beyond the Sun on the 20th

Venus rises at 3 a.m. by the beginning of October, very bright near Regulus in Leo on the 10th, and is furthest from the Sun on the 23rd.  

Mars in Virgo is still out of sight beyond the Sun, until next spring.  Having successfully reached a field of impact craters after a difficult traverse on Mt. Sharp, 1000 feet above the floor of Gale Crater, the Curiosity rover has gone on to reach a feature called the Gediz Vallis Ridge, on August 14th.  It’s a field of boulders, exposed by wind erosion, which originally came down the mountain underwater, in a mud flow landslide about 3 billion years ago, from heights which Curiosity is not expected to reach.  Obviously they’re in a jumble, and areologists  (the Martian equivalent of geologists)  will have a lot of fun sorting them out.

In Jezero crater the Perseverance rover has achieved a similar feat, driving 790 metres across a field of sharp boulders called ‘Snowdrift Peak’, using its Autodrive onboard navigation system, without any control input from Earth.  Meanwhile, nearby, on September 16th the Ingenuity helicopter achieved a new altitude record of 66 feet during its 59th flight.  The next one will take it to 12 times the 5 flights originally planned.    

A late delay has caused the launch of NASA’s Psyche mission, the first to a metallic asteroid, to be postponed to October 12th.  Meanwhile, after its sample return capsule landed in Utah on September 24th, the OSIRIS-REx spacecraft is now on its way to the asteroid Apophis.  Asteroid Bennu, from which the samples were returned, is classed as ‘Potentially Hazardous’ because it could conceivably hit Earth on September 24th, 2182, depending on whether it passes through a ‘keyhole’ near Earth on August 31st, 2135.  The chances of an impact are currently put at one in 2,700  (0.0037%).  But Apophis caused more immediate concern when it was discovered in 2004, because there was initially a 2.7% chance of its striking Earth in 2029, and if it didn’t, there could be a still closer pass in 2036,, whose chances of an impact couldn’t be determined until 2029.  Former Apollo astronaut Rusty Schweickart was among those who argued strongly for a space probe mission to put a transponder on Apophis, to establish by 2017 whether there was a serious danger.  When earlier detections were tracked down, the odds of a 2029 impact came down to 1:45,000, then to 1:250,000, and then to zero,while the chances of an impact in 2068 remain at less than 1:300,000.  Even so, it will pass within the ‘comsat ring’ of communication satellites 22,000 miles up, and OSIRIS-REx won’t reach it until days after the 2029 flyby, so redetermining its orbit after the flyby remains a priority.   

cover of book with asteroids tumbling through space

During the discussions that led to my book Incoming Asteroid!  What could we do about it?  (Springer, 2013), I was often asked why we didn’t focus our attention on Apophis, as many post-2004 studies had done.  We were seeking to answer the question, ‘If we knew there was to be an impact in ten years’ time, what would we do?’, and to do that we had postulated a ‘designer hazard’ which would be a serious threat, but not too hard to reach or too difficult to deal with, with current technology, but soon enough that immediate action was required.  Our project had been running for two years before Apophis was discovered, and it seemed to be a relatively easy target, (stress relatively), in an orbit significantly closer to Earth’s own, with a relatively long timescale for action, compared to the ‘Goldilocks object’ we had visualised.  Also there was uncertainty about its size, with estimates of its diameter ranging between 100 and 400 metres, but all much smaller than our 1-kilometre hazard.  (In January 2013, the best estimate was 325 ±15 metres, determined by ESA’s Herschel space telescope.)  Its composition was equally uncertain – whereas we could be certain about Goldilocks’s size and composition, because we had made them up.  By 2029 we can expect to know a great deal more.  OSIRIS-REx will spend 18 months studying Apophis, and use the same technique to stir up the surface that it did on Bennu.

If the limitation on the mission is onboard propellant or attitude control gas, there may be an option to land on Apophis  (and if so, you heard it here first).  OSIRIS-REx isn’t designed for that, but neither was the NEAR-Shoemaker probe, which landed on the asteroid Eros in 2001.  That was an achievement of the redoubtable Dr. Bob Farquhar  (see ‘Comets and Spacecraft’, ON January 2nd 2022), who did it not only without authorisation but expressly against the wishes of the NASA Director.  By the time the latter got into the control room to stop it, Dr. Farquhar was already receiving telephone congratulations from the US President, who probably thought it was meant to happen all along.

Jupiter rises about 7.00 p.m. in Aries, passed by the Moon on the 1st and 2nd and again on the 28th, when it will make a spectacular companion to the lunar eclipse.  Jupiter is moving retrograde  (westward)  against the stars as the Earth overtakes it, before opposition in November.  Its volcanic moon Io crosses the planet along with its shadow on the 30th, as do Europa and Ganymede at other times.

Saturn in Aquarius set at 2.30 p.m., and the Moon is near Saturn on 23rd and 24th October.  Saturn is still moving retrograde after opposition in August. 

Uranus in Aries rises at 7.00 p.m., following Jupiter, and is 8 degrees from Jupiter in early October, before they separate again.  Uranus appears near the Moon on the 2nd and 30th.

Neptune sets about 5 p.m., in Pisces, moving retrograde after opposition in September.  Neptune is near the Moon on October 26th.

The Orionid meteor shower from Halley’s Comet peaks on the night of 21st-22nd October, and will be unspoiled by moonlight after the Moon sets at 11.30 p.m..  The Southern Taurid shower from Comet Encke peaks on the 10th, again with little moonlight to spoil it, and the Northern Taurid counterpart begins in late October, peaking in November.

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

Categories: Science

Tagged as: , , ,

1 reply »

Leave a Reply