9: Venus

how hot is venus?

• would expect it to radiate heat from sun away with heavy atmosphere (maybe 50-60C)

• in reality it is 420-440C
  due to greenhouse effect

  

Venus clouds and the wind speed

• super high wind speeds

• atmos at cloud level rotates 60x faster than planet 100m/s

• often occurs on rocky planets close to their stars

• rotation = 243 earth days, atmos 4 days

• dense - fluid like

• little water vapour

• water loss in past

  

Venus Geological history

• primary, secondary and tertiary crust

• tectonism

• no knowledge of interior

• venus, earth and mercury formed from a similar part of propoplanetary disk

Why does Venus have no magnetic field?

• slow rotation - lack of internal convection

• any liquid metal portion could not be rotating fast enough

• could have had in past

Why is Venus able to maintain its atmosphere?

The sun has stripped Venus’ atmosphere throughout history as there is no magnetic field to protect it (like earth). However it is not stripped, meaning it must be being replenished (active volcanic outgassing)

Describe the surface of venus

• volcanic activity

• no old terrain

• long lived heating

• no impact craters

• heavily tectonicised - fault systems

What impact craters are present on Venus?

• small not seen: bias as they will be obliterated before surface due to high pressure

• large craters (1000) >25km - young, complex

  

Venus geological timescale names

1. pre-fortunian

2. fortunian

3. guineverian

4. aurelian

   

describe the Pre-Fortunian period

• - predates the observed surface geological features and units

• remnants may exist in the form od deformed rocks and minerals

Describe the Fortunian Period

• GLOBAL TECTONIC REGIME

• lower stratigraphic boundary cannot be determined with the available datasets

Describe the Guineverian period

• GLOBAL VOLCANIC REGIME

• distributed deformed plains

• mountain belts, regional interconnected groove belts

• global emplacement of vaast and deformed plains of volcanic origin

• global wrinkle ridge formation

• 70% resurfaced

descrive the Aurelian period

• NETWORK RIFTING VOLCANISM REGIME

• formation of prominent rift zones and fields of lava flows

• large shield volcanioes

• earlier-formed coronae

• 16% resurfaced

What are Tessera?

• volcanic or sedimentary deposition, folding and erosion, rather than granitic

• covered by younger lava flows

• HEAVILY FOLDED - FORTUNIAN

• 7% venus surface

  

What is planet scale resurfacing

• volcanism period

• GUINEVERIAN AND AURELIAN

• stagnant crustal lid

• innermost mantle likely still convecting

• melting of INTERIOR

what volcano types are on Venus?

• lots

• large d>100km

• 9 sub-groups

• intermediate 20-100km

• small <20km

• rift style

  

Altitude of Venus volcanos?

low

Maat Mons

• aphrodite terra

• low viscosity lava flows

• 395km diameter

  

What are pancake domes?

• viscous lava (more SiO2)

• steep sides, cool skin forms

• inside cools and lava withdraws - fractures

• Domical Hills (tholi)

• shield like

• 25km wide, up to 750m high

• Alpha region

What are canali?

• lava flows into channels

• thermally eroded down into surrounding lava field

• similar to Lunar Rilles

• Runny, low viscosity

  

How to test for volcanism?

• seismometer landing

• thermal spectromeyter

• land on lava flow

• look for themal anomalies

• detect sulfur

• look through clouds for hotter areas

Nocae and Coronae

• volcano tectonic interaction

• 200 on venus

• range from 60-1000km

• plume heads: form over upwellings in mantle of venus - uplifted, circular, extensional faulting

What are Coronae?

• active volcano sites on venus

• ring-like structures around some could indicate activity

• of 133, 37 active in past 2-3Mya

When have new lava flows been detected?

• Magellan feb and nov 1991

• surface appears to have changed

• volcanic vent changed shape

• lava flow formed

  

venus summary

Habitability on Venus?

• need nutrients, water, pressure, temp, ph

what do models suggest about water on venus?

1. DID have stable surface ocean - oldest areas may have minerals present for water - sedimentary rocks - biosignatures

2. DID NOT have oceans - climate modelling

Life in Clouds?

test:

• observations from earth using mm wavelengths of light

• phosphene as biomarker in atmosphere

• evidence of potential absorbtion where phosphene absorbs light

• argument

• scientists prove/disprove

Why is there a new era of Venus exploration?

• 3 new missions

• EnVision: 2031 launch, 6 year cycle

Veritas and Davinci