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Announcements

!  If you are interested in this week’s observing session, please be sure to sign up on Blackboard in advance!  this session will be run by the TA

!  This week’s lecture is available in webcast format only, as I am out of town!  all students are expected to view the webcast, just as

they are normally expected to attend class!  the associated lecture notes are available now at the

usual location on Blackboard!  This webcast will cover the remainder of Chapter 7!  Assignment 7 and Quiz 7 cover Chapter 7

!  both are due on Tue. Nov. 15 at 2 p.m.

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Topics to be Covered in this Webcast

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!  The exploration of Mars (continued)!  The atmosphere of Mars!  The surface of Mars!  Water on Mars!  Review and comparison of the terrestrial planets

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Spirit and Opportunity Rovers!  NASA’s Spirit rover landed in Gusev Crater on Jan. 4,

2004!  NASA’s Opportunity rover landed in tiny Eagle Crater

in Meridiani Planum on Jan. 24, 2004

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Gusev Crater

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Landing on Mars with Airbags!

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The Columbia Hills

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Hematite on Mars

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Opportunity’s Landing Site

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Opportunity & Eagle Crater

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Eagle Crater

The Opportunity rover landed in Eagle Crater, whose rocky outcrops indicate that Meridiani Planum was once an ancient salt-water ocean. 77

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Mars Phoenix Lander

!  Mars Phoenix landed safely in the northern polar region of Mars in May 2008, and carried out experiments for about 3 months

Mars Phoenix Starts Digging

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Mars Curiosity Rover!  More recently, the Mars Curiosity rover arrived on Mars

!  it landed safely on Mars in August 2012!  This rover is much larger and more capable than its

predecessors!  It is looking for the chemical building blocks of life

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Mars Curiosity’s Target: Gale Crater

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The View From Curiosity’s Landing Spot

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ExoMars Rover

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!  In 2021, the ExoMars rover is due to land on Mars!  This rover will be able to extract and analyze samples

from a depth of up to 2 metres!  at this depth, the soil is protected from solar radiation and

from reacting with the Martian atmosphere!  This rover will provide our best shot (so far) at detecting

life in the soil of Mars

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Human Exploration of Mars?

The Challenges of Visiting Mars

!  Mars is certain to be the first planet to be explored by humans, as its surface is quite hospitable, compared to the other planets

!  What are the key challenges that astronauts will face when visiting Mars?!  a round trip of several years or more!  prolonged periods of weightlessness en route!  exposure to high levels of radiation!  the psychological challenges of extreme isolation

!  Sending astronauts (rather than robotic spacecraft) would be extraordinarily expensive

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Inspiration Mars

!  Goal: send 2 humans to Mars in 2021!  The catch: this is a flyby mission

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Mars One

!  Goal: send 4 humans to Mars by 2027!  The catch: this would be a one-way trip!

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The Atmosphere of Mars

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!  Mars has a very thin atmosphere

!  It is made mostly of carbon dioxide (95%)!  it also has some nitrogen,

argon, oxygen and water!  It is thick enough to support

strong winds and huge dust storms

Surface Conditions on Mars

!  The air pressure at the surface of Mars is very low compared with the Earth!  it is about 0.6% of Earth’s air pressure!  astronauts would need to wear pressurized spacesuits

!  However, the surface gravity would be quite comfortable!  about 1/3 of the surface gravity on Earth

!  The average surface temperature on Mars is about -60°C!  the coldest temperatures are found near the poles during

the winter, with temperatures reaching -150°C!  the warmest temperature are found near the equator during

the summer, with temperatures reaching +20°C!  The surface of Mars is very dry and dusty

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Sand Dunes on Mars (credit: Mars Curiosity)

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A Dust Devil on Mars

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A Global Dust Storm on Mars

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Dust Storms on Mars

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The Surface of Mars

!  Many fascinating surface features have been found on Mars, especially by Viking, Mars Global Surveyor, Mars Express, and MRO

!  These features include towering volcanoes, deep canyons, craters, and polar ice caps

!  Mars appears to have been very active geologically, particularly early in its history

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Polar Ice Caps

!  Mars has permanent ice caps at both poles!  they are composed mostly of carbon dioxide (dry ice)

!  In the northern summer, the carbon dioxide disappears, revealing a residual layer of water ice at the north pole

!  The south pole is always covered by a layer of solid carbon dioxide!  this ice caps shrinks during the southern summer, but

never disappears completely!  there appears to be a layer of water ice beneath

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The Southern Polar Ice Cap

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Craters on Mars

Craters are seen in many places on the surface of MarsSome craters have been altered by wind, sand, and ice

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The Topography of Mars

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Olympus Mons

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Mars, as seen by Viking

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Coprates Chasma in Valles Marineris

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Water on Mars

!  Mars is currently very cold and dry, and has little geological activity

!  However, in the past, it appears to have been warm and wet, with active volcanoes

!  Spacecraft which have visited Mars have found numerous lines of evidence that water flowed on Mars in the past, and probably still trickles in places today

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A Dry Riverbed on Mars?

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An Ancient “Crater Lake”?

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Opportunity Finds Sedimentary Layers

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Opportunity Locates Hematite on Mars

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Curiosity Image of a Dried-up Streambed

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Was Mars Covered With Water in the Past?

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Where Has the Water Gone?

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!  As we have seen, there is plenty of evidence to suggest that Mars was wet in the past

!  However, Mars is very dry at present!  Where has the water gone?!  There are several possibilities:

!  it has been lost to space!  it exists on or near the surface as ice!  it exists under the surface as liquid water

!  All of these ideas have been examined recently using orbiters and landers

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Recent Results From MAVEN

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!  The MAVEN satellite has detected the loss of atmospheric particles to space!  75% of this loss occurs within a tail of particles which

flow downstream from the solar wind!  25% of this loss occurs within polar plumes extending

out from the north and south poles

Hydrogen Content (from Mars Odyssey)

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Mars Phoenix Finds Ice

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Seasonal Dark Streaks on Mars

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!  The dark brown streaks on this MRO image appear in Martian spring and summer, and fade away in fall and winter

!  They may have been produced by sub-surface water ice which melts and flows down this crater wall

!  Similar features have been seen elsewhere near the Martian equator, where temperatures rise above the freezing mark

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Life on Mars?

!  It is becoming increasingly clear that Mars had abundant water on its surface billions of years ago

!  It also seems likely that some of this water still exists as a liquid just below the surface

!  Could life have existed early in the history of Mars?!  If so, could some of this life still be present today?

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Review of The Terrestrial Planets

!  We finish this section with a brief review and comparison of the four terrestrial planets

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Terrestrial Planets: Rotation

!  Mercury: 58.7 days (2/3 of a Mercury year)!  Venus: 243 days (retrograde)!  Earth: around 24 hours!  Mars: around 24.5 hours

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Terrestrial Planets: Atmospheres

!  Mercury: no significant atmosphere!  Venus: 96% carbon dioxide!  Earth: 78% nitrogen, 21% oxygen!  Mars: 95% carbon dioxide

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Terrestrial Planets: Surface Temperatures

!  Mercury: -170° C to +430° C!  Venus: averages +480° C!  Earth: averages +15° C!  Mars: -140° C to +20° C

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Terrestrial Planets: Moons

!  Mercury: none!  Venus: none!  Earth: one large moon!  Mars: two tiny moons

(Phobos & Deimos)

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Before Next Class

!  Complete Assignment 7 and Quiz 7!  due on Tue. Nov. 15 at 2 p.m.

!  Read Chapter 8 (The Outer Planets)!  Complete LearningCurve: The Outer Planets

!  due on Thu. Nov. 17 at noon

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