Decembers talk: “Mars, The Prohibition planet” by Dr. J. Wade

Dr Jon Wade of the OU is an example of the mature student who got hooked on Earth Sciences – and has that typical enthusiasm of someone who has come late onto his subject.

Some intriguing stuff for starters:  the nebula history of planet formation goes back to Immanuel Kant, 1755, but it was Pierre-Simon Laplace who supposed that the nebula had to be rotating round the baby Sun, developing concentric rings from which the planets formed.  It appears he got this idea from a rather unusual character, Emanuel Swedenborg, who got the idea from a dream…(look the rest up.)

So we think we know about how gravity caused all nebula bits to coalesce then wham, you have your planetesimals then planets.  But how the little bits of stuff start to aggregate is still not well understood.  Once the bits get bigger then you start to get radioactive decay of Aluminium 26, then the lumps get bigger and differentiation starts, so you get a denser iron rich core and silicates on the surface.  This happens when the lumps get to about 100km across, he says.  Look up Pallasites – odd and lovely meteoritic lumps that have come from these planetesimals where you get iron and silicates (usually olivine) mixed up in them.

There is a lot of rust in this talk:  the cores of Mercury, Earth and Mars are similar but iron in the mantle is hardly seen in Mercury, more in the Earth’s and even more in Mars’ (weight/atomic percentages being roughly 1%, 8% and 18% respectively).  This means that the planets nearer to the Sun lost their oxygen more easily.

So, is core formation the key to planetary habitability?  (His words)  How long did the water last?  How significant is this rustiness?  And why is Mars so lopsided?  Mars’ northern boundary is lower than the southern, which has lots of craters and a high level of minerals that have reacted with water.  The northern bit is an old ocean basin, the result of a massive impact.  It has a long dead volcano 22km in height.  Why no evidence of tectonic activity?  The implication is that there was a lot of water on Mars between about 4 billion years ago and 3.5  billion years ago, which means a lot of sedimentary activity took place on Mars in the first 500 million years of its life.  Its magnetic field was weak, as were its tectonics, and there may have been as much as 3km depth of water at one point.  The presence of the iron (more of his lively speculations) means the water was taken up in the rocks and sediments.  Easy to understand why Mars is the colour it is – yes, it really is the rust – and why the lack of water prevented life from evolving.

Luckily the constant upheavals in the Earth’s mantle mean that new stuff keeps coming to the surface, so it never went the way of Mars.  Copper, nickel, iron, manganese, all stayed stuck deep in Mars’ core.  Iron is very important for life on Earth.  However, we did have a boring billion years (his words) around 2.5 billion years ago, where there was major oxidation (too much iron again) and a large upsurge in methane in the atmosphere, which killed off any attempt at incipient life formation.  Look at the surface basalts.  He says Earth’s core is gradually growing, but that it’s crystallisation that’s keeping the heat going, rather than radioactivity.  He says radioactive elements don’t like staying in the core.

Venus during November

The planet is Venus is visible in the early morning throughout the month of November. It will be highest at the end of the month. Over this time period it will slowly grow from a thin crescent (8.4% of the disk illuminated) 54.4” in angular diameter to a thicker crescent (25% illumination) and a smaller angular diameter of 41.2”. It gets smaller because the planet is getting further away from the Earth as it moves around the Sun.

Clear skies.

 

The Orionids meteor shower 2018

This year the Orinids meteor shower peaks in the predawn skies of October 2st. Orion will be in the south around 4:30am BST an hour after the Moon has set and several hours before Sunrise. The meteors can appear in any part of the sky, but if you trace them back they will appear to originate from the constellation of Orion. For the best views look to the sky about 45 degrees on either side of the constellation from a dark sky location.

The meteors are caused by the Earth moving through the trail of debris left by Comet Halley.

Clear skies

Draconid meteor shower 2018

The Draconids meteor show peaks on the evening of Monday 8th October. See below for a sky chart. The radiant is in the West North West, the best time to look being in the early evening, after 8:30pm BST.

The Draconids are the result of debris from comet 21P/Giacobini-Zinner which will pass close to the Seagull Nebula in the early hours of Tuesday morning, a great photo opportunity.

Clear skies.

Report from our observing session on the 4th October

Well the season has gotten off to a good start, the first observing session scheduled for the year and we are not clouded off as usual!

The new site seemed to be as good, if not better than our old site, slightly less light pollution from Abingdon, but possibly affected by the car lights a little more (if I am to be picky), not as good view to the West but much better to the East and North from the end of the car park we Observed from.

There was 8 of us altogether with 5 telescopes and several pairs of binoculars.

Trevor with his 5” refractor, Keith and Jason both had 8” Celestron Edge HD scopes, Graham had a Celestron C90 and I took my 6” RC. Cristina also had her 15 x 70 Celestron binoculars.

We started off looking at Saturn which was only visible for a few minutes before dipping below some trees to our south west. The rings are in a favourable position at the moment, giving us a lovely view (even if it was only for a few minutes).

Next target was mars, although very bright, it was not a particularly impressive view.

We then attempted to go through some the Deep Sky list that was in the September Space Watch, plus a few others.

M13 Globular Cluster in Hercules, M15 GC in Pegasus and M2 GC in Aquarius.

The Veil Nebula through Trevor’s refractor with an Oxygen 3 filter.

M27 The Dumbbell Planetary Nebula in Vulpecula

M31 Andromeda Galaxy and its 2 companion galaxies M32 and M110

M81 and M82 Bodes Galaxy and the Cigar Galaxy in Ursa Major

M45 The Pleiades, Open Cluster

NGC 869 and NGC 884 The Double Cluster in Perseus

And another Galaxy that Trevor showed us, that I cant remember the name of (but I will edit it in to the report later and no one will be any the wiser 😉)

Altogether it was a very enjoyable evening, clear skies for the duration, lots to look at and nice to get a look through some different scopes and eye pieces.

Hope to see more of you at the next one.

Clear skies