Moon tour
Itwasfunwhileit lasted,butthe50th
anniversaryoftheApollo 11 mission
isnowbehindus.SoonApollowill
revertbacktobeinga historicalevent,
asdistanttosomeastheendofWorld
WarIIortheQueen’scoronation,andin
schoolsacrossthecountry– andacross
theworld– childrenwilllearnabout
theglorydaysofApollointhesame
waytheylearnaboutthetimesofthe
VictoriansortheVikings.
So,halfa centuryafterNeil
Armstrongtookthat“onesmallstep”,
let’stakea lookatanotherfootprinton
theMoon– oratleasta lunarfeature
thatobserversthinklookslikeone...
ThemostcasualglanceattheMoon
througha telescope– orevena pairof
binoculars– willrevealitssurfaceis
coveredwithcraters,holesblastedout
oftheMoonbyasteroidsthatslammed
intoit atincrediblespeedandwith
incredibleforce.Somearehuge,more
thana hundredkilometresacrossand
surroundedbysystemsofbrightrays
ofdustandrockthatsplashedaway
fromthemwhentheywereformed.
Buttherearecountlessnumbersof
smallercraters.Mosthaveonething
incommon:theyareroughlycircular.
Aswithallvalleys
and craters on the
Moon, you’ll get
your best views
of this fascinating
feature when it
is close to the
terminator.Top tip!
After celebrating Neil Armstrong’s small
step, see a giant ‘lunar footprint’
However, a few rebel craters aren’t
circular. They just look... strange.
Our tour destination this issue
is Schiller, a 179-kilometre (111-mile)
long, 71-kilometre (44-mile) wide
impact feature down near the Moon’s
southwestern limb, not all that far
from the bright, ray-sploshed crater
Tycho. It can’t be seen with the naked
eye. You might glimpse it through a
powerful pair of binoculars, but really
you’ll need a small telescope to see it.
On a night when the air is still and the
astronomical ‘seeing’ is good, Schiller
will look more like a gouge or a long
pit than a crater. This is because, being
so far south and so close to the Moon’s
limb, we see it at quite an oblique
angle, so it appears foreshortened. But
it genuinely is an elongated feature:
photographs taken by the Apollo
astronauts and later by orbiting survey
satellites as they passed over Schiller
show why it is so often described by
experienced Moon-watchers as being
‘lozenge-shaped’ or, as we said earlier,
a footprint – albeit the footprint of
someone with long, skinny feet!
When the Moon is full Schiller is
quite hard to find, but when the Sunis hitting Schiller at an angle it really
is a fascinating sight. Then, through a
telescope using higher magnification,
Schiller offers the lunar observer a
visual feast. Its rim is very sharp and
well defined, and its impressively high
walls, which rise some four kilometres
(2.5 miles) from its f loor, are cut
along with stacked terraces, shelves
and ledges. At its western end, two
mountainous ridges jut up from the
centre of Schiller’s floor, neatly splitting
that half of the crater in two. The f loor
of the other half to the east is much
f latter and smoother, a f loodplain of
ancient lava marked by only a couple of
young craterlets.
How did this weird feature form? At
first glance the obvious explanation
is that Schiller was made when a
huge chunk of space debris struck the
Moon at a low angle, ploughing a long
trench out of its surface, and what a
spectacular sight that would have been!
However, those detailed images taken
from above suggest to some lunar
observers that Schiller is not a single
crater, but two craters which formed
when multiple meteoroids smashed
into the Moon almost simultaneously.Howmany?Mostprobablya pair,but
some researchers wonder if Schiller
wasn’t formed by as many as four
separate objects.
However many pieces of space debris
created it, Schiller is fascinating to look
at. So when can you see it this month?
At the start of our observing period
the Moon will be full, so Schiller will
be quite hard to see, little more than a
bright oval-shaped outline close to the
southwestern limb. By 24 August the
terminator – the line between lunar
night and day – will be approaching
Schiller, and it will really stand out
from the surface. On 26 August Schiller
will be plunged into darkness as the
terminator sweeps over it, and we
won’t be able to see it again until 11
September, when the Sun will rise in
its sky and its high walls will cast stark
shadows across the lunar surface again.©
NASASTARGAZER