KECK INSTITUTE FOR SPACE STUDIES

       

Jennifer M. Jackson

Jennifer M. Jackson (California Institute of Technology)

Campus PI


James A. Cutts

James A. Cutts (Jet Propulsion Laboratory)

JPL PI


Co-Investigators:

  • David Stevenson, Victor Tsai, Zhongwen Zhan (Caltech)
  • Suzanne Smrekar, Michael Pauken, Mohammad Mojarradi, Harish Manohara (JPL)
  • David L. Mimoun, Raphael Garcia (ISAE)
  • Philippe Lognonné (IPGP)
  • Gerald Schubert (UCLA)
  • Sebastien Lebonnois (LMD)

Project Participants:

  • Graduate Student: Natalia Solomatova (Caltech)
  • Undergraduate: Tyler Perez (Caltech)
  • Postdoctoral Scholar: Dr. Gregory Finkelstein (Caltech)

Overview

In 2014, we conducted a KISS study entitled “Venus Seismology”, where we explored approaches to developing seismic sensors that can operate at the surface of Venus, as well as alternative techniques that can be implemented high in the atmosphere or in space (Cutts et al. 2015). We laid out a roadmap for technology development, identified technology experiments that could be implemented on missions that are already in the planning phase including New Frontiers, Discovery and ESA’s Cosmic Vision and defined a concept for a dedicated Venus Climate and Interior structure mission as a credible Flagship mission candidate for the next decadal survey. This Technical Development Study represents the next step towards this goal. Building upon the accomplishments of these recently completed KISS studies, we have assembled a team of scientists and technologists from Caltech, JPL, UCLA and three French research institutions to undertake the critical experiments and modeling needed to propose future space flight experiments and ultimately a dedicated mission.

Probing the interior structure of Venus is a formidable challenge but one that has tremendous importance for understanding Venus itself, its relationship to Earth and what that implies for the evolution of Earth-like exoplanets. Our knowledge of the formation, evolution and structure of the terrestrial planets (including Earth) is currently impeded by the very limited understanding of Venus. This unfortunate state of affairs has arisen because Earth's twin planet presents a formidable challenge for in situ investigations. Seismology is a powerful technique that is responsible for much of what we know about the Earth’s interior, has played a key role in characterizing the lunar interior, is about to be applied at Mars with the INSIGHT mission and can play a key role in answering fundamental questions about Venus. However, seismic instruments used at the Moon and Mars will not work under Venus surface conditions (730 K and 90 bars). The goal of the technical development proposal is to devise experimental approaches to investigating the interior of Venus with techniques that can be implemented with achievable technology.

The proposed tasks include methods for both coping with and also exploiting the extreme environment of Venus with its high surface temperatures and pressures.  The observational techniques would require platforms in orbit, on a balloon in the middle atmosphere.

Venus Seismolody

Figure 1. Venus does not exhibit plate tectonics but tectonic and volcanic features must reflect the structure and dynamics of the planet’s interior. Seismic events can be used to probe the structure and on Venus can be observed from three vantage points. The surface platform (left) detects seismic wave in the conventional way but requires sensors and systems that operate at high temperatures for extended periods of time. The balloon platform, operating at altitude of 53–55 km at Earth-like temperatures detects infrasonic waves from Venus quakes. The orbital platform (upper right) acquires a synoptic view of the planet and detects optical and infrared signatures of seismic events.

Theoretical investigation of the role of the Venus atmosphere and atmosphere-surface interaction on seismic studies of the interior of Venus

The dynamic atmosphere of Venus represents both a limitation on the ability to detect small Venus quakes whether from a surface, balloon or orbital vantage point. However, surface-atmosphere interaction also creates an opportunity to characterize the subsurface without the need for quakes using the methods of ambient noise tomography. We will bring together a Caltech campus team with experience in using ambient noise tomography on terrestrial problems with planetary scientists knowledgeable about waves and turbulence in the Venus atmosphere, which will be a primary source of ambient noise on Venus.

Balloon-borne infrasonic measurements

Another major accomplishment of the KISS study was the recognition that Venus quakes will produce strong infrasonic signals that can be detected as pressure waves at altitudes in the Venus atmosphere where long duration observations are possible with existing technology.  The goal of this part of the investigation is to build a sensor assembly that can discriminate infrasonic waves of seismic origin from other sources of pressure variations and to test this sensor on the Earth with a balloon platform that is similar to the one that is planned for Venus.  If successful this technology would be ready for deployment in various Venus mission concepts.

High Temperature Seismometer

The goals of this effort are to develop a seismometer and associated electronics that could function on the surface of Venus and generate data of a sensitivity approaching that which is now possible for Mars. This development capitalizes on the vacuum microelectronics and micromachining capability developed at JPL’s microelectronics laboratory. The near term goal is a sensor which could be deployed on a Venus lander of limited lifetime such as those planned by NASA (New Frontiers VISE) as well as Russia’s Venera D and generate data on the seismic background on Venus that would be vital to the design of a long duration seismic experiment as called out in the Venus Exploration Analysis Groups roadmap of 2014.

Venus mineralogy and geophysical properties

The goals of this investigation are to establish constraints on phase transformations and magnetic properties of candidate Venus crustal materials under relevant Venus crustal conditions. Specifically, these properties are: (1) volumetric collapse that could trigger phase transformational faulting, thus triggering a Venusian quake, (2) magnetic ordering changes that will predict future magnetometer observations that will be used in modeling of Venus’ crust and interior. The focus of this new research program is to investigate the physical and chemical properties of complex environments of crystal minerals saturated with different atmospheric compositions at pressures and temperatures expected on the surface and subsurface of Venus. The presence of these gases in silicate- and clay-rich rocks would lead to crucial interactions with these phases.

1 Probing the Interior Structure of Venus, Report by Keck Institute for Space Studies (KISS) Venus Seismology Study Team, Mar 31, 2015

Description: Jennifer Jackson and graduate student Natalia Solomatova conducting measurements of candidate Venus analogues, at the Advanced Photon Source

Jennifer Jackson and graduate student Natalia Solomatova conducting measurements of candidate Venus analogues, at the Advanced Photon Source

Description: Networking at the 2015 Space Connection: Jennifer Jackson, Jessica Watkins (GPS Chair's Postdoctoral Scholar; AGEP Fellow), and future Venusians

Networking at the 2015 Space Connection: Jennifer Jackson, Jessica Watkins (GPS Chair's Postdoctoral Scholar; AGEP Fellow), and future Venusians


2016 Progress Update

Venus mineralogy and geophysical properties (Lead: Jackson)

Postdoctoral scholar Gregory Finkelstein (Postdoc in Mineral Physics with Jackson) and Natalia Solomatova (graduate student in Mineral Physics with Jackson) have begun experimental work establishing constraints on phase transformations and magnetic properties of candidate Venus crustal materials under relevant Venus crustal conditions. Specifically, these properties are: (1) volumetric collapse that could trigger phase transformational faulting, thus triggering a Venusian quake, (2) magnetic ordering changes that will predict future magnetometer observations that will be used in modeling of Venus’ crust and interior. (Figures 1-3). Starting this summer, SURF undergraduate: Tyler Perez (2nd year student in Planetary Science, Caltech) will work with Dr. Finkelstein and myself on observing phase transitions in hydrated basaltic compositions at elevated pressures and temperatures.


Figure 1. Synthesized glasses under reducing conditions (at the iron-wüstite buffer), by M. Roskosz.


Figure 2. Mössbauer spectroscopy: tholeitic basalt glass with preliminary fitting results is as follows: Site 1: Isomer shift (IS)=0.98 mm/s and quadrupole splitting (QS)=1.70 mm/s and Site 2:IS=0.53 mm/s and QS=0.93 mm/s. More detailed spectral analysis is ongoing.


Figure 3. The hydrothermal diamond anvil cell for recreating deep crustal conditions on Venus.

Theoretical investigation of the role of the Venus atmosphere and atmosphere- surface interaction on seismic studies of the interior of Venus (Leads: Schubert, Lebonnois, Garcia)

A major accomplishment of the KISS study was the recognition that Venus quakes will produce strong infrasonic signals that can be detected as pressure waves at altitudes in the Venus atmosphere where long duration observations are possible with existing technology. Progress towards this end includes the numerical modeling (finite difference simulations) of atmospheric acoustic and gravity waves created by seismic surface waves propagating in Venus interior is performed in a windy and attenuating atmosphere model provided by latest GCM simulations of S. Lebonnois. The atmosphere is forced from below by the Venus surface with dispersive surface waves propagating at 4 km/s.  Our study will focus on the effects of the strong winds present in Venus atmosphere on the acoustic wavefront.

Balloon-borne infrasonic measurements (Leads: Cutts, Pauken, Mimoun)

Another major accomplishment of the KISS study was the recognition that Venus quakes will produce strong infrasonic signals that can be detected as pressure waves at altitudes in the Venus atmosphere where long duration observations are possible with existing technology. Activities include: modeling the wave propagation (1 PhD student, 2 undergraduate students), understanding the background noise  (2 undergraduate students), and preliminary terrestrial balloon experiment instrument design  (1 engineer, 2 undergraduate students). Microbarometers have been secured and are undergoing acceptance tests. Venus atmospheric models are provided by S. Lebonnois’ work (see above section).

High Temperature Seismometer (Leads: Manohara)

The goals of this effort are to develop a seismometer and associated electronics that could function on the surface of Venus and generate data of a sensitivity approaching that which is now possible for Mars. This development capitalizes on the vacuum microelectronics and micromachining capability developed at JPL’s microelectronics laboratory. The near term goal is a sensor which could be deployed on a Venus lander of limited lifetime such as those planned by NASA (New Frontiers VISE) as well as Russia’s Venera D and generate data on the seismic background on Venus that would be vital to the design of a long duration seismic experiment as called out in the Venus Exploration Analysis Groups roadmap of 2014. Progress towards this end includes: A complete sensors trade study, while developing designs and analyses of JPL sensors and amplifier electronics as applicable to Venus. We are also working on fabricating and testing of the Field Emission (FE)-microseismometer concept, as well as fabricating and testing CNT vacuum tube amplifier.