b'6 Carnegie Science|Summer 2019Its the Inside that Counts in Planetary HabitabilityThe heart of habitability is in planetary interiors.Life on Earth depends on the dynamics ofWithout a magnetic field, we would be the interior says a team of Carnegiebombarded by dangerous cosmic radiation.investigators, published in aScience We need a better understanding of howessay. The teams expertise ranges froma planets composition and interior influences geochemistry and planetary science toits habitability, starting with Earth, Shahar astronomy. They urge the researchsaid. This can be used to guide the search forThe research group, top and bottom left to right, includes community to recognize the vitalexoplanets and star systems where life couldCarnegies Anat Shahar, Peter Driscoll, Alycia Weinberger, importance of a planets interior in creatingthrive and with signatures that could beand George Cody. They explore which of Earths features were essential for the origin and sustenance of life, and an environment thats hospitable for life.detected by telescopes.how scientists can identify those features on other worlds.The group, including Carnegies AnatIt begins with the formation process. Shahar, Peter Driscoll, Alycia Weinberger,Planets are born from the rotating ring ofplanetary interior conditions, and and George Cody, explores which of Earthsdust and gas surrounding a young star.mathematical modeling and simulation. features were essential for the origin andThe elemental building blocks from whichCarnegie scientists are long-established sustenance of life and how scientistsrocky planets formsilicon, magnesium,world leaders in the fields of geochemistry, identify those features on other worlds.oxygen, carbon, iron, and hydrogenaregeophysics, planetary science, astrobiology, With existing capabilities, observinguniversal. But their abundances and theand astronomy, Weinberger said. So, our an exoplanets atmospheric compositionheating and cooling they experience willinstitution is perfectly placed to tackle this will be the first way to search foraffect interior chemistry and, in turn,cross-disciplinary challenge. signatures of life elsewhere. However, thefeatures like ocean volume andIn the next decade, as a new generation of Carnegie team argues that a true picture ofatmospheric composition.telescopes come online, scientists will begin to planetary habitability must consider howOne of the big questions we need tosearch in earnest for biosignatures in the a planets atmosphere is linked to andask is whether the geologic and dynamicatmospheres of rocky exoplanets. But Shahar shaped by its interior.features that make our home planetand her colleagues say that these observations Earth is the only planet in the Solarhabitable can be produced on planets withmust be put in the context of a larger System with plate tectonics, which is crucialdifferent compositions, Driscoll explained. understanding of how a planets total makeup for maintaining a surface climate where lifeThe Carnegie colleagues assert thatand interior geochemistry determines the can thrive. Whats more, without the cyclingthe search for extraterrestrial life must beevolution of a stable and temperate surface of material between the surface and interior,guided by an interdisciplinary approachwhere life could arise and thrive. the convection that drives the Earthsthat combines astronomical observations,The heart of habitability is in planetary magnetic field would not be possible.laboratory experiments mimickinginteriors, concluded Cody.Mid-AtlanticRidgeInterplanetary Magnetic Field LinesSouth AmericaMagnetosheathSpin AfricatransitionzoneMagnetotailBow ShockLower Dmantle Outercore InnercoreLife on Earth depends on the dynamics of its interior, where material circulates via convection, left. Earth is unique in the Solar System with its plate tectonics. The movement of the plates contributes to the cycling of material between the surface and the interior. Without this cycling, the convection that drives the Earths magnetic field, right, would not be possible.And without a magnetic field, we would be bombarded by dangerous cosmic radiation. Left image courtesy Sergey Lobanov; right image courtesy NASA/Goddard/Aaron Kaase'