Europa Study 2012 Report - Solar System Exploration - NASA

707 Pages·2012·55.7 MB·English

National Aeronautics and Space Administration
EUROPA STUDY 2012 REPORT

Europa Study Team, 1 May 2012, JPL D-71990
Task Order NMO711062 Outer Planets Flagship Mission Cover art Michael Carroll
National Aeronautics and Space Administration
EUROPA STUDY 2012 REPORT
EXECUTIVE SUMMARY
Europa Study Team, 1 May 2012, JPL D-71990
Task Order NMO711062 Outer Planets Flagship Mission Cover art Michael Carroll
EUROPA STUDY 2012 REPORT EXECUTIVE SUMARY
ES. EUROPA STUDY 2012 REPORT: EXECUTIVE SUMMARY
Contents
ES  Europa Study 2012 Report: Executive Summary .................................................................................. 2 
ES.1  Executive Summary .................................................................................................................. 2 
ES.1.1  Introduction ................................................................................................................ 2 
ES.1.2  Habitability of Europa as Motivation for Future Missions ........................................... 3 
ES.1.3  Europa Mission Study ................................................................................................ 4 
ES.1.4  Orbiter Concept ......................................................................................................... 5 
ES.1.5  Multiple-Flyby Concept .............................................................................................. 7 
ES.1.6  Lander Concept ....................................................................................................... 10 
ES.1.7  Key Architectural Concepts ...................................................................................... 13 
ES.1.8  Cost Estimating Methodology .................................................................................. 14 
ES.1.9  Independent Review ................................................................................................ 15 
ES.1.10  Summary ................................................................................................................. 16 

This research was carried out at the Jet Propulsion Laboratory, California Institute of Technol-
ogy, under a contract with the National Aeronautics and Space Administration, with contribu-
tions from the Applied Physics Laboratory, Johns Hopkins University.

The cost information contained in this document is of budgetary and planning nature and is
intended for informational purposes only. It does not constitute a commitment on the part of JPL
and/or Caltech.
ES-1
Copyright 2012. All rights reserved. Government sponsorship acknowledged.
EUROPA STUDY 2012 REPORT EXECUTIVE SUMARY
ES. EUROPA STUDY 2012 REPORT:
EXECUTIVE SUMMARY
ES.1 Executive Summary
ES.1.1 Introduction
Four hundred years ago, Galileo’s discovery of
Jupiter’s four large moons forever changed
humanity’s view of the universe, helping to
bring about the Copernican Revolution. Today
one of these Galilean moons may again
revolutionize science and our sense of place,
for hidden beneath Europa’s icy surface is the
most promising home for extant extrater-
restrial life within our reach.
This new appreciation began to unfold in
1995, when a spacecraft named in Galileo’s
honor arrived at the Jupiter system to follow
Figure ES.1.1-1. Europa’s surface shows a landscape
up on earlier Voyager discoveries. As part of
scarred by tectonic and icy volcanic events. This image
its mission, the Galileo spacecraft could
of the Conamara Chaos region at 11 m per pixel implies
provide only tantalizing samplings of data
that portions of the surface have been broken up into
at Europa (Figure ES.1.1-1); nonetheless, it
giant plates. This event is inferred to have happened in
provided strong evidence for a deep global
Europa’s geologically recent past. The dark reddish
ocean beneath Europa’s icy crust, leading to
material may be derived from the ocean.
speculation on the potential for life within icy
moons. By 2008, technical studies culminated in a
mature Pre–Phase A mission concept, the
Meanwhile, over the last quarter century we
Jupiter Europa Orbiter (JEO), as part of a joint
have learned that Jupiter-like planets are
NASA–ESA Europa Jupiter System Mission
common around other stars, and perhaps many
(EJSM). The JEO concept was further refined
have icy moons like Europa. Understanding
throughout 2009 and 2010 in a pre–Phase A
Europa—one of the most geophysically
mode. The March 2011 Planetary Science
fascinating and astrobiologically promising
Decadal Survey concluded that the science
bodies in our solar system—is therefore vital
contribution of such a mission would be of
to understanding the habitability of worlds
paramount importance, comparable to the
throughout the galaxy.
entire proposed Mars Sample Return cam-
A mission targeting Europa would be needed paign. It stated, “Because of this ocean’s
to pursue these exciting discoveries using potential suitability for life, Europa is one of
close-up observation with modern instrumen- the most important targets in all of planetary
tation designed to address the habitability of science” (Space Studies Board 2011, p. 271).
Europa. Over the last decade, NASA has
However, because of serious concerns over
considered several mission options for explor-
mission cost, based on NASA’s independent
ing Europa, convening a series of Science
cost estimate, the Decadal Survey also rec-
Definition Teams (SDTs), composed of
ommended that “NASA should immediately
experts from the scientific community, to hone
undertake an effort to find major cost reduc-
the highest priority science objectives for
tions for JEO, with the goal of minimizing the
Europa.
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EUROPA STUDY 2012 REPORT EXECUTIVE SUMMARY
result from reactions between the seawater and
the warm rocky ocean floor.
Life as we know it depends on three principal
“ingredients”: 1) a sustained liquid water
environment; 2) essential chemical elements
(e.g., C, H, N, O, P, S) that are critical for
building life; and 3) a source of energy that
could be utilized by life (Figure ES.1.2-2). For
Europa, current assessment of these three
Figure ES.1.2-1. Europa is believed to have a relatively
broad requirements for life can be summarized
thin ice shel above a 100-km-thick global ocean—
equivalent to twice the volume of all of Earth’s oceans— as: 1) a likely internal global ocean, which has
in direct contact with a rocky mantle below. Oxidants likely existed for over 4 billion years, and
from the surface above and chemicals from the rocky potentially water pockets within the ice shell;
mantle below might be able to supply the ocean water 2) elements derived from the primordial
with the required chemistry and energy for life.
chondritic composition of the satellites, plus
delivery by asteroids and comets over time;
size of the budget increase necessary to enable
and 3) oxidants at the surface, and possible
the mission” (Space Studies Board 2011, p. 5).
hydrothermal activity at the ocean floor as
To that end, NASA Headquarters promptly
driven by tidal heating, suggesting that the
enlisted a new Europa SDT, and directed
cycling of chemical energy into Europa’s
the Europa Study Team to examine a set of
ocean over geological time is vital to under-
reduced-scope options for exploring Europa.
standing its habitability.
Independent cost and technical reviews were
These “ingredients” and the scientific issues
to be performed on all study results. What
surrounding them define three themes of
follows is a summary of these results.
water, chemistry, and energy that permeate
ES.1.2 Habitability of Europa as discussions of Europa’s potential habitability.
Motivation for Future Missions
Europa may meet these minimum require-
Europa is a prime candidate in the search for
present-day habitable environments in our
solar system. Europa is unique among the
large icy satellites (Figure ES.1.2-1) because it
probably has a saltwater ocean today beneath
an ice shell that is geodynamically active and
relatively thin (several kilometers to several
tens of kilometers thick). The combination of
irradiation of its surface and tidal heating of its
interior could make Europa a rich source of
chemical energy for life. Perhaps most im-
portantly, Europa’s ocean is believed to be in
direct contact with its rocky mantle, where
conditions could be similar to those on Earth’s

biologically rich sea floor. Hydrothermal
Figure ES.1.2-2. The three “ingredients” for life—water,
zones on Earth’s seafloor are known to be rich
chemistry, and energy—are key to understanding
with life, powered by energy and nutrients that
Europa’s habitability, and they are developed into
themes that permeate the Europa mission concepts.
ES-3
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EUROPA STUDY 2012 REPORT EXECUTIVE SUMMARY
ments, but the processes that shape Europa’s a combined Jet Propulsion Laboratory (JPL)
ice shell, and the exchange processes between and Applied Physics Laboratory (APL) study
the surface and ocean, are poorly understood. team performed the technical work.
Indeed, even the existence of a subsurface
The SDT was tasked with reformulating the
ocean, while suspected, is not yet proven. With
science of a Europa mission to achieve
this in mind, the four categories of scientific
compelling science while ensuring reduced
investigation most relevant to understanding
risk and scope from past studies. The SDT
Europa’s habitability are:
approached the task by identifying an over-
Ocean: Existence, extent, and salinity of the arching goal, key science objectives, and
ocean and its relation to the deeper interior; science investigations to best address those
objectives, with examples of appropriate
Ice Shell: Existence and nature of any subsur-
measurements that could be carried out at
face water within or beneath the ice shell,
Europa to address the science investigations.
heterogeneity of the ice shell, and the nature of
surface-ice-ocean exchange;
The SDT determined that there is a clear
Composition: The chemistry and distribution division among the key science questions and
of salts, any organics, and other compounds, associated investigations (Table ES.1.3-1),
and their relationships to ocean composition; where some are best conducted from Europa
orbit, others best achieved through multiple
Geology: The characteristics and formation of
flybys, and the remainder best addressed
surface features, including sites of recent or
through a landed mission. To characterize the
current activity, and implications for water
extent of the ocean and its relation to the
reservoirs and satellite evolution.
deeper interior, scientists need systematic
ES.1.3 Europa Mission Study
geophysical measurements of gravity, topog-
To address and answer the key questions about raphy, and magnetic field: measurements best
Europa’s habitability, a dedicated Europa obtained from an orbital platform. An orbital
mission would be required. To that end, a platform also permits uniform geological
study was conducted starting in April 2011 to mapping. In comparison, observations to
define options for Europa mission concepts. A characterize the ice shell, understand the
Europa SDT guided the science definition, and surface composition, and perform high-
Table ES.1.3-1. Key Europa science questions and associated mission platforms.

✓ Mission concept explicitly addresses the science question.
* Relevant science could be addressed with modest mission modifications.
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EUROPA STUDY 2012 REPORT EXECUTIVE SUMMARY
resolution targeted geological observations are A Europa Orbiter Mission would chiefly
data-intensive and require high-mass, high- perform geophysical measurements (“water”
power instruments, so these are best carried science). A Europa Multiple-Flyby Mission
out from a spacecraft that makes multiple would concentrate on performing remote
flybys of Europa, transmitting data back to measurements that address the “chemistry”
Earth during long orbital petals. Only a lander and “energy” science. A Europa Lander
could accomplish evaluation of the detailed Mission would concentrate on in situ “chemis-
surface chemistry and mineralogy to best try” science.
understand the detailed nature of near-surface
ES.1.4 Orbiter Concept
organics and salts, as these investigations
ES.1.4.1 Orbiter Science
require in situ sample analyses.
The orbiter concept is tailored to the unique
Any of these three mission options would
geophysical science that requires being in orbit
provide high caliber, compelling science that
at Europa. This includes confirming the
would change paradigms in our understanding
existence of an ocean and characterizing that
of the nature and habitability of icy worlds.
ocean through geophysical measurements of
Each is intended to fly completely inde-
Europa’s gravitational tides and magnetic
pendently, without a requirement for any other
induction response. It also includes mapping
mission.
of the global morphology and topography of
Each mission option has a common goal:
the satellite, to reveal its geological evolution.
Explore Europa to investigate its
habitability. The objectives, investigations, and model
planning payload of the Orbiter Mission are
Table ES.1.4-1. Objectives, investigations, and model planning payload for a Europa Orbiter concept.
Note: Shaded check marks illustrate that the objectives directly address the themes of water (W), chemistry (C), or energy (E).
ES-5
Copyright 2012. All rights reserved. Government sponsorship acknowledged.