ASTR 380: Possibilities for Life in the Inner Solar System - Midterm Results and Venus - P, Study notes of Astronomy

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ASTR 380

Possibilities for Life in the Inner Solar System

ASTR 380

Midterm Test Results

Generally people did well:

100 - 90 = A

= 19 people

89 – 80 = B = 19 people^ 79 – 70 = C =

9 people

69 – 60 = D =

0

< 60

= F =

1 person

For total course so far… estimate from homework (30%)

and mid-term exam (70%):

100 - 90 = A =

14 people

89 – 80 = B =

24 people

79 – 70 = C =

6 people

69 – 60 = D =

3 people

< 60

= F =

3 person

Last Lecture: the Moon, Mercury and the Moons of Mars.Now we will look at Venus (this lecture) and Mars (next)

Chapter 7 and Chapter 10.

Remember: We have only visited the Moon with people.

We only have rocks from the Moon to study on Earth!

We are examining the possibilities in these next few lectures.

Possibilities for Life in the Inner Solar System• Seeing what existing evidence says• What we can infer• Few 100% conclusions

Possibility of Life in the Inner Solar System

The Moon, Mercury, and the Moons of Mars

Deimos Phobos

Moon

Mercury

NO LIFE NOW or EVER

This is a 98% conclusion!

Possibility of Life in the Inner Solar System

The Moon versus our checklist:

chemical building blocks: light on amounts of C, N, and Oenergy: lots of sunlightliquid: No. And no atmospherestability: Except near poles, 29 day day-night cycle

average day temperature = 107 Caverage night temperature = -153 C

Possibility of Life in the Inner Solar System

The Mercury versus our checklist:

chemical building blocks: 70% metallic and 30% silicate

may have lost much C, N, O in a late largecollision.

energy: lots and lots of sunlightliquid: No. Nearly no atmospherestability: Due to 59 day long rotation (Mercury day)

and very slight atmosphere…

night time lows = -183 Cdaytime highs = 427 C

Possibility of Life in the Inner Solar System

The Moons of Mars versus our checklist:

chemical building blocks: Carbonaceous asteroids so

good C,N,O energy: reasonable sunlightliquid: No. No ices. No atmospherestability: Probably reasonable but no data on temperature

variations as specific locations on Moons

Possibility of Life in the Inner Solar System

The Moon, Mercury, and the Moons of Mars

Deimos Phobos

Moon

Mercury

NO LIFE NOW or EVER

This is a 98% conclusion!

Possibility of Life in the Inner Solar System

What do we know about Venus?Cloud covered at all times!Mass = 0.815 Earth massSurface Gravity = 0.91 EarthAverage Density = 5.25 g/cm

3

Distance from Sun = 0.723 AU

Possibility of Life in the Inner Solar System

What do we know about Venus?Energy from Sun = 1.9 x EarthNo MoonsEquatorial radius = 0.95 Earth“Expected Temperature” = 350 K

= 77 C

Possibility of Life in the Inner Solar System

Possibility of Life in the Inner Solar System

Venus has been visited by probes:Mariner 2 flyby in 1962

• measured surface temperature• tried to measure magnetic field Venera 3 crashed into planet in 1966 - no data returned Venera 4 entered atmosphere in 1967 and parachuted down

but died before getting to the ground.

• measured composition of atmosphere and pressure

Mariner 2

Possibility of Life in the Inner Solar System

Mariner 5 fly by a 4,000 km above atmosphere in 1967

• Measured pressure profile of atmosphere Venera 5 and 6 (1969) entered atmosphere,

descended and were crushed about20 km above surface

• returned more atmospheric data Venera 7 (1970) supplied temperature data

from the surface for 23 minutes.

Venera 8 (1972) send surface temperature

data for 50 minutes.

Mariner 5

Possibility of Life in the Inner Solar System

Venera 10

Mariner 10 (1974) flyby with images of

clouds.

Venera 9 and 10 (1975) sent back

the first images of the surface.

• images • surface temperature, pressure, wind

Possibility of Life in the Inner Solar System

Venera 11

Venera 11 and 12 (1978) Venera 13 and 14 (1982) made

first color picture of surface

Venera 13

Possibility of Life in the Inner Solar System

Venera 15

Venera 15 and 16 (1983) did radar mapping

of surface from orbit.

Russian Vega Program (1985) put two

areobots (balloons) in atmosphere.Second lasted for 2 Earth days.

• Atmosphere temperature, pressure,

winds.

Magellan Probe (1990-1994) mapped surface of Venus

with radar imaging

Venus Express (European – 2006 to present) imaging

the clouds on Venus from Orbit.

Possibility of Life in the Inner Solar System

Venus Express imageStudy:cloud structurewindscompositiontime variations

Possibility of Life in the Inner Solar System

Magellan radar imageof the surface ofVenusRadar can seethrough theclouds tomeasure thealtitude of theland Light colors arehigher altitude.

Possibility of Life in the Inner Solar System

Magellan simulated imageof surface from radaraltitude data

Color artistic

choice

Possibility of Life in the Inner Solar System

What have we learned from the probes?

• Most of the surface of Venus is covered by old lava

flows but there appears to be little current activity.

• There are rocks, mountains, and canyons• No evidence of liquid water now or in past. No ice• Impact craters – It is suggested that the

surface may be only 500-700 Myrs old

• No plate tectonic activity• Surface Temperature = 460 C – and nearly constant

Possibility of Life in the Inner Solar System

What have we learned from the probes?

• Surface pressure = 92 bar

= 92 times Earth

• Composition

CO

: 96.5% 2

N

: 3.5% 2

SO

: 0.015% (^2) Ar: 0.007% H^2

O: 0.002%

CO: 0.0017%He: 0.0012%Ne: 0.0007%

• Strong winds and clouds

Possibility of Life in the Inner Solar System

CO

and the runaway Greenhouse! 2 Thick carbon dioxide atmosphere traps the infrared radiation^ 460 K^ versus^ 350 K

Possibility of Life in the Inner Solar System

Why is there so much CO

? 2

Venus and Earth should have formedin the same way from nearly thesame material – should have samerock and gas composition….But…. Earth had….The collision that made the Moon --stripped early Earth atmosphere.And liquid water -- geologicalprocesses to lock CO2 into rocks

Possibility of Life in the Inner Solar System

The water problem – Venus is dry, very dry! Yes, it is hot so you wouldn’t expect liquid water….. But Venus appears to have 1/10,000 as much water as Earth! Why? Perhaps…. Water is in water vapor which rises to the top of the atmosphere – is split – and hydrogen escapes… Factors: hot, close to Sun,

and no magnetic field

Possibility of Life in the Inner Solar System

Terra-forming Venus Problems to solve:

Too hot Too much CO2 Too little water?