Proposed NASA mission to a moon of Saturn
Voyager 2
view of Enceladus in 1981:
Samarkand Sulci
vertical grooves (lower center);
Ali Baba
and
Aladdin
craters (upper left)
Enceladus Life Finder
(
ELF
) is a proposed
astrobiology
mission concept for a
NASA
spacecraft intended to assess the
habitability
of the
internal aquatic ocean
of
Enceladus
, which is
Saturn
's
sixth-largest moon
[1]
[2]
of at least 146 total moons, and seemingly similar in chemical makeup to
comets
.
[3]
The spaceprobe would orbit Saturn and fly through Enceladus's
geyser-like
plumes
multiple times. It would be powered by energy supplied from
solar panels on the spacecraft
.
Overview
[
edit
]
Enceladus's south pole - Geysers spray water from many locations along the
'tiger stripes'
feature.
The Enceladus Life Finder mission was first proposed in 2015 for
Discovery Mission 13
funding,
[2]
and then it was proposed in May 2017 to NASA's
New Frontiers program
Mission 4,
[4]
[5]
[6]
but it was not selected.
[7]
If selected at another future opportunity, the ELF mission would search for
biosignature
and
biomolecules
in the geysers of Enceladus. The south polar jets loft water, salts and
organic molecules
dozens of miles over the moon's surface from an underground regional ocean. The hypothesis is that the water is warmed by thermal vents similar to features found deep in Earth's oceans. ELF's instruments would measure
amino acids
? the building blocks of
proteins
? analyze
fatty acids
, and determine whether
methane
(CH
4
) found in the plumes could have been produced by living
organisms
.
[2]
In 2008, the
Cassini
orbiter was flown through a plume and analyzed the material with its neutral
mass spectrometer
. The orbiter detected simple organics, including methane (CH
4
),
carbon monoxide
(CO),
carbon dioxide
(CO
2
)
nitrogen
, and complex
organic compounds
.
[8]
Cassini
also detected sodium and potassium at a concentration implying a salty liquid ocean.
[8]
However,
Cassini
did not have the equipment with the sensitivity required for direct analyses.
[1]
[8]
On 14 December 2023, astronomers reported the first time discovery, in the
plumes
of Enceladus, of
hydrogen cyanide
, a possible chemical essential for
life
as we know it, as well as other
organic molecules
, some of which are yet to be better identified and understood. According to the researchers, "these [newly discovered] compounds could potentially support extant
microbial communities
or drive complex
organic synthesis
leading to the
origin of life
."
[9]
[10]
Mission concept
[
edit
]
Composite map of Enceladus's south polar region showing cracks dubbed
'tiger stripes'
where the geysers are located.
The Enceladus Life Finder (ELF) mission would pursue the implications of
Cassini
orbiter's 2005 discoveries of active jetting from, and existence of an ocean within, Enceladus. The mission concept would have the ELF orbiter fly 8 to 10 times over a period of 3 years through plumes of water launched above the south pole of
Enceladus
.
[2]
The geysers could provide easy access for sampling the moon's subsurface ocean, and if there is
microbial life
in it, ice particles from the sea could contain the evidence
astrobiologists
need to identify them.
[11]
The Principal Investigator is
Jonathan Lunine
of
Cornell University
in Ithaca, New York.
Objectives
[
edit
]
The goals of the mission are derived directly from the most recent decadal survey: first, to determine primordial sources of
organics
and the sites of
organic synthesis
today; and second, to determine if there are current
habitats
in Enceladus where the conditions for
life
could exist today, and if life exists there now.
[1]
To achieve these goals, the ELF mission has three objectives:
[1]
- To measure abundances of a carefully selected set of neutral species, some of which were detected by
Cassini
, to ascertain whether the organics and volatiles coming from Enceladus have been thermally altered over time.
- To determine the details of the interior marine environment —
pH
,
oxidation state
, available chemical energy, and temperature — that permit characterization of the life-carrying capacity of the interior.
- To look for indications that organics are the result of biological processes through three independent types of chemical measurements that are widely recognized as diagnostic of life.
Proposed scientific payload
[
edit
]
Artist's impression of possible
hydrothermal activity
on Enceladus.
The ELF spacecraft would use two
mass spectrometers
to assess
habitability
of the interior oceanic environment. The payload consists of
the MASPEX and the ENIJA, optimized to analyze respectively the gas and grains:
[1]
[8]
The
Cassini
spacecraft
has measured small
silica
particles, normally formed at 90 °C or higher, streaming from Enceladus.
[12]
The size and composition of the particles suggest that they come from current
hydrothermal activity
,
[13]
[14]
[15]
[16]
where the moon's ocean meets the underlying rock, a prime habitat for life.
[12]
[17]
ELF's instruments would conduct three kinds of tests in order to minimize the ambiguity involved in life detection.
[1]
[8]
The first would look for a characteristic distribution of
amino acids
(the building blocks of
proteins
). The second test would determine whether the
carbon
number distribution in
fatty acids
or
isoprenoids
is biased toward a particular rule (even, odd, or divisible by a small integer). The third would measure carbon and
hydrogen
isotopic ratios
, together with the abundance of
methane
relative to other alkanes, to assess whether the values fall in the range for biological processes.
[8]
See also
[
edit
]
References
[
edit
]
- ^
a
b
c
d
e
f
Lunine, Jonathan I.; Waite, Jack Hunter Jr.; Postberg, Frank; Spilker, Linda J. (2015).
Enceladus Life Finder: The search for life in a habitable moon
(PDF)
. 46th Lunar and Planetary Science Conference (2015). Houston (TX): Lunar and Planetary Institute.
- ^
a
b
c
d
Clark, Stephen (April 6, 2015).
"Diverse destinations considered for new interplanetary probe"
.
Space Flight Now
. Retrieved
April 7,
2015
.
- ^
Battersby, Stephen (March 26, 2008).
"Saturn's moon Enceladus surprisingly comet-like"
.
New Scientist
. Retrieved
April 16,
2015
.
- ^
Cofield, Calla (April 14, 2017).
"Enceladus' Subsurface Energy Source: What It Means for Search for Life"
.
Space.com
.
- ^
Chang, Kenneth (September 15, 2017).
"Back to Saturn? Five Missions Proposed to Follow Cassini"
.
The New York Times
.
- ^
Mann, Adam (2017).
"Inner Workings: Icy ocean worlds offer chances to find life"
.
Proceedings of the National Academy of Sciences
.
114
(18): 4566?4568.
Bibcode
:
2017PNAS..114.4566M
.
doi
:
10.1073/pnas.1703361114
.
ISSN
0027-8424
.
PMC
5422794
.
PMID
28461387
.
- ^
Glowatz, Elana (December 20, 2017).
"NASA's New Frontier Mission Will Search For Alien Life Or Reveal The Solar System's History"
.
IB Times
.
- ^
a
b
c
d
e
f
Lunine, Jonathan I.
"Searching for Life in the Saturn System: Enceladus Life Finder"
(PDF)
.
ELF Team
. Lunar And Planetary Institute
. Retrieved
April 7,
2015
.
- ^
Chang, Kenneth (December 14, 2023).
"Poison Gas Hints at Potential for Life on an Ocean Moon of Saturn - A researcher who has studied the icy world said "the prospects for the development of life are getting better and better on Enceladus."
"
.
The New York Times
.
Archived
from the original on December 14, 2023
. Retrieved
December 15,
2023
.
- ^
Peter, Jonah S.; et al. (December 14, 2023).
"Detection of HCN and diverse redox chemistry in the plume of Enceladus"
.
Nature Astronomy
.
arXiv
:
2301.05259
.
doi
:
10.1038/s41550-023-02160-0
.
Archived
from the original on December 15, 2023
. Retrieved
December 15,
2023
.
- ^
Gronstal, Aaron (July 30, 2014).
"Enceladus in 101 Geysers"
.
NASA Astrobiology Institute
. Archived from
the original
on August 16, 2014
. Retrieved
April 8,
2015
.
- ^
a
b
Witze, Alexandra (March 11, 2015).
"Hints of hot springs found on Saturnian moon"
.
Nature News
. Retrieved
April 7,
2015
.
- ^
"Ocean Within Enceladus May Harbor Hydrothermal Activity"
.
SpaceRef
. March 11, 2015.
- ^
Platt, Jane; Bell, Brian (April 3, 2014).
"NASA Space Assets Detect Ocean inside Saturn Moon"
.
NASA
. Retrieved
April 3,
2014
.
- ^
Iess, L.; Stevenson, D. J.; Parisi, M.; Hemingway, D.; Jacobson, R.A.; Lunine, Jonathan I.; Nimmo, F.; Armstrong, J. W.; Asmar, S. W.; Ducci, M.; Tortora, P. (April 4, 2014).
"The Gravity Field and Interior Structure of Enceladus"
(PDF)
.
Science
.
344
(6179): 78?80.
Bibcode
:
2014Sci...344...78I
.
doi
:
10.1126/science.1250551
.
PMID
24700854
.
S2CID
28990283
.
- ^
Amos, Jonathan (April 3, 2014).
"Saturn's Enceladus moon hides 'great lake' of water"
.
BBC News
. Retrieved
April 7,
2014
.
- ^
Anderson, Paul Scott (March 13, 2015).
"Cassini Finds Evidence for Hydrothermal Activity on Saturn's Moon Enceladus"
.
AmericaSpace
. Retrieved
April 7,
2015
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