MARS 4 TH ROCK FROM THE SUN MARTIN STEVENS HALESWORTH U3A OCTOBER 2106

Transcription

1 MARS 4 TH ROCK FROM THE SUN MARTIN STEVENS HALESWORTH U3A OCTOBER 2106

2 MARS CAN BE SEEN BY THE NAKED EYE

3 SOME BASICS THINGS WE LIKELY KNOW Fourth plant from the sun -- second smallest after Mercury -- and Pluto was downgraded Named after Roman god of war - Great tune by Holst Often called the Red Planet -- has reddish appearance A terrestrial planet ( rocky) like The Earth Has a thin atmosphere Has impact craters like the moon -- and desserts and polar ice caps as does earth

4 MORE THINGS WE KNOW Goes around the sun quite like earth Has tilt on it s axis like earth causing seasons like earth Has 2 small moons - much smaller than ours Can easily be seen from earth with naked eye - looks red -- only Sun,Moon Jupiter and Venus are brighter

5 MARS AND MOONS RELATIVE SIZES

6 MARS -- PHYSICAL CHARACTERISTICS Approximately half diameter of Earth BUT it s dry land area is very similar to Earth no oceans / rivers / lakes Less dense than Earth about 15% of the Earth volume an 11% of it s mass. -- this results in lower surface gravity about 38% of that on Earth. Red/Orange predominant colour caused by rust (iron oxide) Other colours when you get there -- seen are, golden, brown,tan, greenish- depending on minerals present

7 MARS --- TEMPERATURE Surface Temperature From minus 143C to plus 35C --- mean minus 63Celcius In old money -- minus 226 F to plus 95Fahrenheit -- one of the reasons why there is no liquid water -- more later

8 MARS -- WHAT S IT MADE OF? CORE AND CRUST Structure like Earth - it has a dense metallic core and an outer / overlaid crust Interior core thought to be made primarily of Nickel and Iron -- plus 16% Sulphur Crust -- silica mantel that forms many of the surface features tectonic and volcanic plus collisions But now seems dormant -- no active volcanos / tectonic movement Crust is about 31 miles thick on average Earth crust is about 25miles thick taking size or Earth and Mars into account earth crust is only a third as thick Most abundant elements found in crust -- silicon, oxygen, iron, magnesium, aluminium, calcium, and potassium

9 MARS -- THE SURFACE Largely made up of volcanic rock -- like basalt (Giants Causeway come to mind) Covered in a rusty (iron oxide ) fine grained dust that blows about in the wind more later About 60% of surface shows evidence of external impacts (craters) with likely more evidence hidden below Likely from the so called Late Heavy Bombardment period after formation which all solar system planets were subject to. One theory is that a Pluto sized body impacted some 4 Billion years ago - causing the Borealis Basin which covers 40% of the surface

10 MARS -- GEOLOGICAL HISTORY SHORT VERSION Three primary periods Earliest --Noachian period 4.5 to 3.5 billion years ago surfaces scarred by many impact craters Formation of a volcanic upland Tharsis bulge Flooding by LIQUID water late in the period

11 GEOLOGICAL HISTORY 2 Hesperian period billion years to 2.9/3.3 billion years ago Marked by formation of extensive lava plains -- hence earlier craters underneath! Amazonian period ---- Few impact craters More lava flows CURRENT activity? 2.9/3.3billion years ago to now - not quite dead some evidence of minor lava and water flows, and avalanches from cliffs

12 MARS AND EARTH - TILT AND ROTATION

13 MARS CLIMATE 1 Mars has the most earth like climate in the solar system - due to similar tilts on their rotational axis Martian seasons are about twice those of earth - further from the sun AND takes 2 earth years to go round the Sun. Greater distance from sun than earth ( 1.52) results in just 43% of sunlight falling on it per unit area. More pronounced ellipse in orbit than earth earth more circular - has pronounced effect on climate --- this results in

14 MARS CLIMATE 2 The seasons in the south being more extreme than the seasons in the north The north is therefore milder than it would be if Mars had a more circular orbit Summer temperatures in the south can hit 30C /54F ---- ice would melt! More later Mars has the largest (iron oxide/rust) dust storms in the Solar System vary from small areas to the whole planet Tend to occur when Mars closest to the Sun -- and can increase global temperature

15 POLAR ICE CAPS /2000 North pole South pole

16 MARS -- POLAR CAPS Like Earth Mars has 2 polar ice caps During its winter they are in permanent darkness -- cause 25% of the atmosphere to become slabs of dry (carbon dioxide ) ice. When warming frozen carbon dioxide COs sublimes (to change directly from a solid to a vapour or gas without first melting ) creating enormous winds that sweep off the poles at up to 250 mph Causes Earth like frost and cirrus clouds red dust storms. Both caps compose 70% water ice and then on north cap top a thin layer of seasonal carbon dioxide - dry ice -- south cap has permanent thicker dry ice cover

17 LIFE ON MARS? HABITABILITY -SEARCH FOR LIFE Planetary Habitability ---- the ability of a world to develop environmental conditions favourable to the emergence of life Current understanding is it Favours planets with LIQUID water on their surface 2. Requires the orbit to lie within habitable zone -- for our Solar System extends just beyond Venus to part of the where Mars just dips into on part of its journey around the Sun

18 HABITABILITY 2 BUT Mars thin atmosphere prevents liquid water existing over large area for extended periods. It evaporates as well as mostly too cold Past water flows demonstrate planets habitability potential BUT recent evidence suggests Martian surface water to have then been too salty to support regular terrestrial life Lack of a magnetosphere (Definition of magnetosphere. : a region of space surrounding a celestial object dominated by the object's magnetic field so that charged particles are trapped in it.) and thin atmosphere mean there little heat transfer across the planet -- poor insulation against solar winds and insufficient atmosphere for water to remain as a liquid turns to vapour (steam) Geologically dead (or almost) meaning little chemical mixing /recycling.

19 HABITABILITY 3 -- TIMES PAST? Investigations by two of the Mars Rovers suggest that that Mars was once more habitable than today However whether living organisms ever existed their remains unknown The soil nutrients found would be able to support life BUT it would still need to be shielded from the intense UV light so that only highly reflective or sub surface organics would have been able to have survived

20 MARS THE 2 MOONS

21 MARS THE 2 MOONS Phobos ( Greek - fear /panic) 14 miles across and Deimos (Greek terror/dread) 7.5 miles across which orbit close to the planet Phobos has an unstable descending orbit looks like a recent capture AND may crash onto the Mars surface in 50 million years Asteroid capture remains a long-favoured theory - unlike our Earth Moon which came from Earth Discovered 1877 Composition is more like that of asteroids than Mars

22 MARS EXPLORATION Dozens of spacecraft have been there orbiters, landers and rovers From Russia,USA, Europe and India to study the surface,climate, and geology Currently 7 active probes on or circulating Mars sending data back to Earth Latest from India reached Mars orbit September first successful Asian planetary mission Planned--- Small cubesats now on the way European Space Agency orbiter 2016 and lander 2018 UAE -- planned 2020 /1 orbiter - study the Mars atmosphere Human Missions? -- No active plan has an arrival date before so maybe.

23 MARS - IMPORTANT RECENT OBSERVATIONS 2005 radar data reveals large quantities of water ice and at the poles and elsewhwere 2007 mars rover Spirit finds chemical compounds containing water molecules 2008 Phoenix lander samples water ice in shallow soil 2015 NASA announces presence of briny salt water on surface

24 SOME OLDER OBSERVATIONS - SCIENTIFIC HISTORY Ancient Egyptians recorded a wandering object in sky and by 1534BC aware of its retrograde motion Babylonians astronomers made regular observations - for Mars they worked out it did 42 circuits of the Zodiac every 79 years length of the Martian year 4 th C BC Aristotle worked out Mars went behind our moon - making it further away Known to Chinese astronomers by 4C BC and Indian astronomers by 5C BC 1610 AD - Mars first observed using a telescope --- Galileo

25 MARTIAN CANALS -- LOST IN TRANSLATION 1877 Giovanni - Milan made an early detailed map of Mars - contained what he called cainali - supposedly long straight lines - to which he gave names of well known earth rivers. Canali - mistranslated into canals - a scientific myth was born - the canali later found to be an optical illusion Seasonal changes and apparent canals lead to long held belief in vast seas and vegetation By 1909 better telescopes dismissed this and the canals BUT even up to 1960s papers were written speculating detailed scenarios for the metabolism and chemical cycles for a functioning ecosystem were published. War of the Worlds IS FICTION folks!

26 MARS A THOUGHT TO FINISH ON

27 ANY QUESTIONS?

28 MARS - ANSWERS What is the retrograde motion of Mars caused by? Sometimes the planets appear to change direction in the sky. This retrograde motion is entirely an illusion caused by the Earth passing the slower moving outer planets.