glaze venus-colloquium talk 917 - school of earth … · venus today (at sunrise)! 9/27/17 asu -...

Venus: The Forgotten, Mysterious Planet

Dr.LoriS.GlazeNASA’sGoddardSpaceFlightCenter

September 27,2017

Why are we so fascinated by Venus?• Venuswasoneofthefirst

‘wanderers’ identifiedbyearlyastronomers;importantinmanyearlymythologies

• Venusisthebrightestobjectinthenightsky(otherthanthemoon)

• UniqueinthewaysheappearstojumpfromeveningtomorningskyandinhowinsyncsheiswithEarth:13Venusyears=8Earthyears

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Botticelli’s“BirthofVenus”: bornofthefoamfromtheseaafterSaturncastratedhisfatherUranusandhisbloodfelltothesea.

Venus today (at sunrise)!


VenusiscurrentlytheMorningStar- Augustwaspinnacleofcurrentvisit- Venusrisesacouplehoursbefore

sunrise

VenusdisappearsinDecember- Notvisiblefor2monthswhileshe

passesbehindthesun

VenusastheEveningStar- VenuswillreappearinFebruaryin

theeveningsky

Venus fun facts• VenusisalmostthesamesizeasEarth(85%

Earth’sradius;91%Earth’sgravity)• Venus’“day” islongerthanits“year”

– 1“year”=225Earthdays– 1“day”=243Earthdays– Almostperfectlyspherical

• Venusrotatesbackward(retrograde)• Venushasnoseasons

– Venus’ rotationaxisisclosetovertical(relativetoorbitalplane)

• Venushasnomagneticfield9/27/17 ASU - SchoolofEarthandSpaceExploration 4

Venus shrouded in continuous cloud cover

Venus’ atmosphere: Earth’s evil twin?


Only 10% of incident sunlight reaches the surface.Surface visibility is like Earth on a very cloudy day.

VerystronggreenhouseeffectAtmosphereis96.5%carbondioxide

LikeapressurecookerSurfacetemperature=860˚F(460˚C)meltslead!Surfacepressure=92barislikebeing~½miledeepocean!

FerociouswindsWindspeed=>250mph60xVenusrotationrateAllwest,allthetimeOnly~2mi/houratthesurface

Corrosivesulfuricacidclouds~15milesthick

Despite similar origins, sizes and masses,Venus and Earth evolved differently:

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Earth: Cool and WetVenus: Hot and Dry

When and

Why?

Dailydoseofcolor.com9/27/17 ASU - SchoolofEarthandSpaceExploration 7

> 3,500 Exoplanets have been confirmed(as of 9/20 [NASA Exoplanet Archive] – growing every day)

Hundreds of these exoplanets are in the Earth-Venus-Mars size range. But, data

are lacking to understand where these planets fit along evolutionary pathways.

Brief history of Venus exploration


• Venera(USSR;1961- 1983)– Multipleprobes/landers



• PioneerVenus(US;1978-1992)– Orbiter




• PioneerVenus(US;1978-1992)– Orbiter&probes





• Vega(USSR/Europe;1985)– Lander&2balloons






• Magellan(US;1989- 1994)– Orbitingradar







• VenusExpress(ESA;2006– 2014)– Orbiter,cloudchemistry&dynamics







• VenusExpress(ESA;2006– 2014)– Orbiter,cloudchemistry&dynamics

• Akatsuki(JAXA;2015– ?)– Orbiter,meteorology&lightning


What we’ve learned so far...Venus & Earth have been volcanically active,

but the tectonics are very different

Earth: Plate TectonicsVenus: One “Plate”9/27/17 15ASU - SchoolofEarthandSpaceExploration

Venus does not have plate tectonics

What does the surface look like?


Venera 13 surface image

Theonlydirectviewsoflocal-scalegeologyarefromVeneraimages,acquired>30yearsagoforfourlandingsites inthevolcanicplains

Because ofthethickcloudcover,theonlyglobal imageswehaveofVenusarefromradar– difficulttointerpret

Venus’ surface: Mystery history• 80% of the surface is volcanic

plains (basalt, from Venera)• Fewer than 1000 impact craters

– All are fresh & randomly distributed

• Average age of plains is 500 million years old – everywhere – Was this a “recent” global

resurfacing?

• “Tesserae” are high-elevation, complex ridged terrains– Noknownanaloginoursolarsystem.


Have the surfaces of Venus and Earth always been so different?

Revealed by Magellan Radar

What are tesserae?Appeartobe“older” thantheplainsbasedonstratigraphy


Infrared data from Venus Express[Gilmore et al., 2015]

Elemental chemistry and mineralogy could distinguish mafic versus felsic origin.

FormationofEarth’scontinentsrequiredplatetectonicsANDoceans.WhatdoesthismeanforVenus?

Aretheyadifferentkindofrock?Maybemoresilica-rich,likeEarth’scontinents?

VenusExpressseemstoindicateyes

Planets in our Solar System


Core

Crust

Atmosphere

Mer

cury

, Plu

to, M

ars

& st

uff

Graphic borrowed from Kevin Zahnle

Venu

s &

Earth

Neptune& Uranus

Jupiter & SaturnDid Venus and Earth start out the same?

Origin of Venus’ atmosphere• Neonandargon:ConsistentwithEarthandVenusbeingmadefromsamestuff

• Krypton:Storyfallsapart!– PioneerandVeneradiscrepantbyafactorof15

• Xenon:Nomeasurementsofanykind!!– CriticaltounderstandifVenus’originwasdifferentfromEarth,setting itoffonauniquepath


Figure after Baines et al. [2013]

Noble Gas Inventories

How recently was Venus an ocean world?Deuterium/Hydrogen enables transformational understanding of oceans on Venus

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Venus today Venus 4Ga? 1Ga?ASU - SchoolofEarthandSpaceExploration

Need new water measurements!


Off the chart!

If we can get a better measurement of the water today, we can use models to determine when Venus lost its water to space.

AmountofwaterlossinVenus’atmosphereisstillcontroversial

Pioneermeasurementwasmadeafterinletwascloggedwithsulfuricaciddroplet(only1msmt)

VenusExpressmeasurementsabovetheclouds(~70km)areasmuchas3xgreaterthanthosefromPioneer

What ‘drives’ the Venus atmosphere?


If we can learn how to model Venus’ atmosphere, we can better predict Earth’s future.

VIRTIS 5 µm - infrared

VMC 0.365 µm - ultraviolet

Venus’ south polar vortex, as viewed by two instruments on Venus Express

VenusExpressobservedclouddynamics

Modelscannotexplainwhycloudsmovesofast

Wedon’tunderstandhowthesun’sinteractionwithcloudparticles(aerosols)affectsthechemistryanddynamicsoftheatmosphere

50%ofincidentUVlightisabsorbed– bywhat??

75% of the atmosphere is unexplored!• Veryfewmeasurements below30km• Chemicalprocessescompletelyunconstrained inthelowest15kmoftheVenusatmosphere

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Guesses based on models

Earth for

scale

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How do the surface and atmosphere interact?

ProposedbyBruceFegley

Understanding the role of trace gases on Venus helps put limits on natural climate drivers.


Whatroledotracegasesplay?– SO2,H2O,OCS,H2S

Howarethesulfuricacidcloudsmaintained?

Canchemicalweatheringofthesurfaceprovidethesulfur?

Isanactivevolcanicsourcerequiredtosupplysulfur?

Is Venus still volcanically active?


If so, could we tell?

Artist’s rendition of active volcanoes on Venus

Venus’interiorshouldstillbehot(likeEarth)

– Because VenusandEarthareaboutthesamesize

Earthlosesmostofitsheatatplateboundaries

HowdoesVenusloseheat?– “Heatpipe”volcanoes?– Periodic“overturn”events?– Canthesetypesofeventsbethesourceofsulfur?

Evidence for “current” volcanism?


Pioneer Venus Orbiter/Ground-Based

Venus Express What caused “spikes” in sulfur dioxide?

Ø Pioneer Venus (1978) and Venus Express (2007) both saw spikes

Ø Seen at the cloud tops - 43 miles high (70 km)

Models can predict how much water and sulfur we should be looking for and where.

Sulfur dioxide at the cloud tops

What can provide “pulse” of SO2?

9/27/17 ASU - SchoolofEarthandSpaceExploration 28Pinatubo, 1991

OnEarth,thelargestplumesriseto20-25miles altitude (35-40km- 4xhigherthancommercialaircraftfly)

OnVenus,verydifficulttodriveaplumetocloudtopaltitudes becausethelowestatmosphere issohotanddense

Otherhypotheses:– Periodicoverturnevent intheclouds?

– Meteorite disturbance?

Largeexplosivevolcaniceruption?

Other possible evidence?

VenusExpressobservedunusualanomaliesinsurfacereflectancenearvolcanoes

9/27/17 ASU - SchoolofEarthandSpaceExploration 29Ganiki Chasma [Shalygin et al., 2015]

Idunn Mons [Smrekar et al., 2010]

“younger” surfacesatpotentially activevolcanoes

Anomalies thatcomeandgoinplausiblyvolcanicallyactiveareas

NASA’s “Discovery”

Program• TheDiscoveryprogramsupportssmall($500M)missions:

– DAWN,GRAIL,MESSENGER,MarsPathfinder,Kepler,InSight….

• NASAholdsacompetitioneveryfewyearsforplanetarymissionconcepts– 28conceptssubmitted in2015competition– Fiveselected for9monthstudy: 2Venus(includingDAVINCI)+3asteroid– LucyandPsyche(bothasteroidmissions) selected tofly



Probemissionfocusedon:Ø NoblegasesØ Compositionoftheatmospherebelow12kmwhere2/3ofatmosphericmassresides(unexplored)

Ø AtmosphereinteractionwiththesurfaceØ Tesseramorphology

NASAsupports~2medium($1B)missionsperdecade(3sofar):v NewHorizonsencountered PlutoinJuly2015v Juno iscurrentlyinorbitatJupiterv OSIRIS-REx isen routetoBennu tocollectsample; arrivesAugust2018

Venusisoneof6targetsallowedinthecurrentcompetition(28April2017)v 13proposalssubmittedv 3Venusconcepts proposed(including VICI)

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VICI:VenusInsituCompositionInvestigationsLandermissionfocusedonunderstandingVenusthroughtimebymeasuring:

Ø NoblegasesØ Atmospherecompositionbelow12kmwhere2/3ofatmosphericmass

resides(unexplored)Ø AtmosphereinteractionwiththesurfaceØ Tesserachemistry,mineralogy,&morphology


International Opportunities?Other agencies are also thinking about Venus

(but no firms plans)

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Currentcallfor“Medium”classmissionsisunderway

EnVision isaVenusorbiterwithradarandinfraredspectrometer

Developingaconceptcalled“Venera-D”(long-lived)

NASAisfundingUSparticipationinajointUS-RussianScienceDefinitionTeam

Missionincludesorbiters,aerialplatforms,andlanders

EUROPE

RUSSIA

Earliestlaunchprobably late2020soreven2030

Ifselected,probablywouldn’tlaunchuntillate2020s

In Summary


After6orbitalmissionssince1978,aninsitumissionisneededtoprovidenewobservationsofVenus:

Ø tounderstandtheformationandevolutionofrockyplanets,Ø includingplanetsoutsideoursolarsystem

• VenusisverysimilartoEarthinmanyways,but…• Venusevolvedverydifferently• Wedon’tyetunderstandwhenorwhyVenusevolutiondivergedfromEarth,butweneedto

• TherearecurrentlyNOplannedVenusmissionsbyanyinternationalspaceagency

glaze venus-colloquium talk 917 - school of earth … · venus today (at sunrise)! 9/27/17 asu -...

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