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Executive Summary

Our goal in the Astrobiology of the Icy Worlds Investigation is to advance our understanding of the role of ice in the broad context of astrobiology through a combined laboratory, numerical, analytical, and field investigations. Icy Worlds team will pursue this goal through four major investigations namely, the habitability, survivability, and detectability of life of icy worlds coupled with “Path to Flight“ Technology demonstrations. We will also use a wealth of existing age-appropriate educational resources to convey concepts of astrobiology, spectroscopy, and remote sensing, and especially how these area interplay for learning new information; develop standards-based, hands-on activities to extend the application of these resources to the search for life on icy worlds. Our classification of “icy world” extends to planets, dwarf planets and small solar system bodies composed of a significant fraction (≥10%) of H₂O under conditions of pressure and temperature that sustain water ice. By this definition, all objects of interest in the Solar System are smaller than Earth – though icy “ocean planets”(Leger et al., 2004) may exist around other stars. Glaciated regions of Mars and Earth resemble icy worlds, and these regions will serve as important analogues.

Icy worlds may harbor the greatest volume of habitable space in the Solar System. Beneath their icy surfaces, oceans and seas have been predicted for at least six worlds beyond Earth, yielding a total reservoir of some 30-40 times the volume of all the liquid water on Earth. Such worlds may be habitable if they host biogenic elements and mechanisms for maintaining chemical disequilibria. But the presence of life in these worlds is of little scientific value if our robotic and human explorers cannot discover the inhabitants. The floating shells of icy worlds serve as our only window into the interiors of these worlds – at least for near-future exploration. It is therefore critical to gain an understanding of what signs of life – or biosignatures – may survive on the surfaces or near surface zone of such worlds. The search for such signs requires instruments and techniques capable of detecting them. Advancing this capacity for discovery on other worlds can only be done through well-coordinated laboratory, field, and airborne campaigns of life here on Earth. It is through such campaigns, and an integrated approach to the habitability, survivability, and detectability of life on icy worlds, that we can advance astrobiology and further NASA’s capabilities for discovering life elsewhere while improving our understanding of life here on Earth.

Moving away from the Sun, water ice is ubiquitous on the Earth and beyond. A search for life linked to the search for water should naturally “follow the ice”. As mentioned above, such an approach leads to massive subsurface oceans, which evoke a sense of mystery not unrelated to that familiar to Earth’s global ocean. Can life emerge and thrive in a cold, lightless world beneath hundreds of kilometers of ice? And if so, do the icy shells hold clues to life in the subsurface? These questions are the primary motivation of our science investigations which are as follows:

• Habitability of Icy Worlds investigates the habitability of liquid water environments in icy worlds, with a focus on what processes may give rise to life, what processes may sustain life, and what processes may deliver that life to the surface.

• Survivability of Icy Worlds investigates the survivability of biological compounds under simulated icy world surface conditions, and compare the degradation products to abiotically synthesized compounds resulting from the radiation chemistry on icy worlds.

• Detectability of Icy Worlds investigates the detectability of life and biological materials on the surface of icy worlds, with a focus on spectroscopic techniques, and on spectral bands that are not in some way connected to photosynthesis.

• Our technology investigation, a Path to Flight for astrobiology, utilizes instrumentation built with non-NAI funding to carry out the science investigations discussed above. The search for life requires instruments and techniques that can detect biosignatures from orbit and in-situ under harsh conditions. Advancing this capacity is the focus of our Technology Investigation.

Habitability of Icy Worlds investigation has three major objectives. Objective 1, Seafloor Processes, explores conditions that might be conducive to originating and supporting life in icy world interiors. To enable prediction testing by this and other teams pursuing related questions, we will define biomarker production and look for ground-truth in analog terrestrial systems. Objective 2, Ocean Processes, investigates the formation of prebiotic cell membranes under simulated deep-ocean conditions, computationally assesses the distribution of material and heat through the ocean and ice shell, and seeks to improve relevant chemical literature through a set of high-pressure equation-of-state experiments. Objective 3, Ice Shell Processes, investigates astrobiological aspects of ice shell evolution. Experimental work examines the creation of clathrate hydrates. Computational modeling of ice shell convection tracks the shuttling of these and other biorelevant materials between oceans and surfaces, and also examines the possibility of “sub-glacial” lakes as briny oases within the ice.

One of the highlights of this investigation is related to Seafloor Processes where we test through comprehensive laboratory studies the theory that life may have emerged ~4 billion years ago within porous and partly permeable submarine, moderate-temperature (≤100°C) alkaline hydrothermal springs on any wet, rocky planet or satellite in the Solar system, of sufficient size to have sustained a semi-molten interior early in its history. Based on predictions from this theory, we designed, built and employed a hydrothermal reactor at JPL to simulate hydrothermal vent conditions and analyze the solid and fluid products of reactions between carbon dioxide (in oceans) with hydrogen and ammonia (in alkaline hydrothermal solutions). Five successful reactor runs have been carried out, with which we have shown that (i) HS- can be produced from the interaction of hot hydrogen-bearing alkaline solution with metal sulfides, (ii) up to 16 ppmv CH₄ is generated from 10 bars of CO₂ plus 100 bars H₂ (preliminary data) and (iii) no acetate is produced. These results have important implications for life detection on other wet, rocky worlds such Mars and Europa, which require a source of reductants to couple with oxidants produced at their surfaces. This scenario forms an energetic basis for pre-biotic metabolism, as discussed in multiple publications by Dr. Russell and colleagues, and in a review article recently submitted to Nature by Drs. Vance and Hand.

Another accomplishment is related to the progress made on the effects of low temperature and high pressure on the chemistry of icy world ocean solutions. Investigators, Steve Vance of JPL and Michael Brown of University of Washington developed a method for encapsulating an aqueous ammonia sample without a concern for contamination by hydraulic fluid. Vance and Brown continued analysis of previously acquired sound velocities in water and magnesium sulfate and additional sound velocities for water were acquired which will be incorporated into chemical models such as FREZCHEM.

As far as ice shell processes are concerned, investigators, Matthew Choukron and Christophe Sotin examine the creation and stability of clathrate hydrates. Methane clathrates were found to be increasingly unstable with the addition of ammonia to aqueous solutions to an extent larger than previously expected. The comparison of these new experimental data with thermal models of Titan’s interior has suggested a new model for storage and cryovolcanic release of methane on Titan, which is discussed in a forthcoming publication in Icarus. This work is crucial to improving our understanding of exchanges involving volatiles within icy satellites, and the role of clathrates in storing potential light-molecular-weight nutrients and biomarkers.

As part of our Survivability of icy Worlds investigation, we examine the similarities and differences between the abiotic chemistry of planetary ices irradiated with ultraviolet photons (UV), electrons, and ions, and the chemistry of biomolecules exposed to similar conditions. Can the chemical products resulting from these two scenarios be distinguished? Can viable microbes persist after exposure to such conditions? These are motivating questions for our investigation.
Investigator Murthy Gudipati and his group have focused on investigating the photodegradation of PAH molecules in ices using pyrene as the probe. They find that organics are easily ionized and degraded, but unique product formation is not seen in the UV-VIS spectra shown below, indicating that there may be a wide variety of products with no specific absorption features being formed in the ice.
As a part of Survivability, investigators Paul Johnson, Robert Hodyss and Isik Kanik have begun studying the photo-destruction of organic molecules in icy matrices relevant to solar system bodies. We are measuring the photolytic life times of hydrocarbons in both water and nitrogen matrices. They are also studying the photolytic chemistry of amino acid degradation (using glycine as a test case) through matrix isolation experiments. Their preliminary results indicated that nearly complete destruction of the amino acids has occurred by radiation. The major photolytic mechanism appears to be decarboxylation as evidenced by the existence of the CO₂ peak at 2342 cm-1. Preliminary experiments on photolytic lifetimes of 10% hydrocarbon in N2 ice (at 17K), has been conducted.

The half-life of simple hydrocarbons such as C₂H₂, C2H₄ and C₂H₆ were measured and found to be on the order of 10-40 minutes under the radiation flux of 1 × 1015 photons/cm2s and in the 130 to 334 nm wavelength range.

Detectability of life investigation has three major objectives: Detection of Life in the Laboratory, Detection of Life in the Field, and Detection of Life from Orbit. As far as Detection of Life in the Laboratory is concerned, investigators Kevin Hand and Robert Carlson have been setting up the BioSpec database, a resource for spectra in the NIR and MIR of microbial isolates. Currently, a variety of protocols and procedures are being tested so as to yield the best and most reproducible spectra.

In the area of Detection of Life in the Field, there are two major programs which were initiated during the spring and summer months of 2009. First, our program to spectroscopically map snow algae (primarily C. nivalis)in the Sierra Nevada mountains and to understand the underlying biogeochemistry of these ecosystem began with a small field campaign in June. The team of investigators led by Kevin Hand of JPL spent three days mapping, sampling, and excavating snowfields in the Mt. Conness region of the Sierra Nevada to address is that of why the blooms occur where they do and what controls the onset and distribution of the blooms. By digging a latitudinal trench across an algae-rich snowfield (Figure 3.3) we began work on the depth profile distribution which will help determine the liquid water distribution with the snow, perhaps a controlling factor over the C. nivalis distribution. We have begun analysis of our surface spectra and to date we have a partial map of the algae concentration across the first 2.5 meters of the surface of the transect.

Our second major initiative is the combined climate-change/spectral biosignatures project. As part of this work, we will be mapping the magnitude and distribution of methane and natural gas release on both local and regional scales across the permafrost and lakes. A small team of Investigators began work in some of these lakes around Barrow, AK in mid-August. The team became familiar with operations at the Barrow Arctic Science Consortium and established many important relationships that will help facilitate future work. Samples and data were collected from Ikroavik lake and these will serve as an important baseline for future expeditions that will primarily occur during months when the region is covered in snow and ice.

As a part of Detection of Life from Orbit, Co-I’s Hand and Painter was able to get flight time on the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) which came at no cost to our NAI project. Data were collected over the Sierra Nevada mountains in the region where the team had conducted ground based work. AVIRIS data 'quick-look’ of the region mapped. We are currently waiting for the calibration files and full data set from the AVIRIS team.

Path to Flight Investigation (Investigation 4) has four major objectives. They are 1. Verify measurements of chemicals formed and consumed in laboratory simulations of alkaline hydrothermal vents and modify those measurement instruments into ones capable of shallow depth measurements at a natural alkaline vent (near Iceland). 2. Perform non-invasive biochemical and organism measurements inside deep polar ice cores archived at the National Ice Core Lab (Colorado) and Montana State University. 3. Modify existing set of field instruments to enable their use in major field campaigns around Barrow, Alaska and in snow fields in the western United States. 4. Support special, ad-hoc field activities that might arise as the result of synergistic, cooperative research opportunities with other NAI centers.

As a part of Path to Flight investigation, the advancement of the two Targeted UV Chemical Sensors (TUCS) at 224 and 248 nm to examine the appearance of any organic material from the simulated vent chemistry (Investigation 1) has been completed. Those two instruments have been in modification for several months, adjusting their field-of-view overlapped zones of detection and adjusting the bandpass filters to have greater spectral discrimination and diminished adjacent band leakages. With the high pressure window addition to the laboratory hydrothermal reactor we will accommodate the TUCS to monitor organic compounds generated by the reactor.

As a part of the Biological Material in Ice Cores investigation, jointly conducted with Co-I John Priscu we have completed the required biological analytical assays to measure ice cores resident at Montana State. This effort is to provide a 'ground-truth’ calibration of UV and UV Raman spectral signatures that can be directly related to specific classes of biological material and biochemical ‘waste’ products that would be formed from in situ biological activity.

In support of Survivability Investigation, we are using 'sculpture’ ice blocks as a surrogate for ice cores, and organically clean ultrasonic drills with melt water aspiration, we have drilled 6 to 8 mm diameter holes 5 to 10 cm deep while maintaining an empty drill hole. These serve as test targets for the 2D scanner. By inoculating organics (amino acids, fatty acids, proteins) and bacteria within these holes at variable concentrations, we can test sensitivity of the UV fluorescence and UV Raman instruments This data will also serve as the UV signatures library with will support the future Barrow, Alaska field work and the scanned ice core studies.

Advancement of compact rectilinear ion-trap mass spectrometer (RIT-MS) with an addition of electrospray ionization unit is now completed. The instrument is now fully “field-portable” and capable of carrying out tandem mass spectroscopy measurements (MS5). A manuscript describing this instrument along with the laboratory measurements demonstrating the capability is now in submission for publication.

FY09 was the first year for the Icy Worlds NAI, and as such, it was a year of introductions and beginnings for Education and Public Outreach (E/PO) Program. E/PO staff met with Icy Worlds scientists and with other NAI E/PO leads, to determine how best to design E/PO for this NAI. We established contacts with teachers who are interested in receiving NASA E/PO materials, and began design of astrobiology-related E/PO materials. The highlight of the year was the trip to Barrow, Alaska, where scientists and E/PO leads established contacts at the field research site and met with science teachers and principals at the local schools.

On May 18-19, 2009, Rachel Zimmerman-Brachman and Kevin Hand attended the NASA Astrobiology Institute E/PO Retreat at NASA’s Ames Research Center. We met other NAI E/PO leads, and learned about other E/PO strategies being used at other NAI’s to share their science with students and the public. The Icy Worlds E/PO team worked with Daniella Scalice to update NAI Central with E/PO activities, and we shared ideas for NAI trading cards with other NAI E/PO leads. We participated in monthly NAI E/PO WebEx videoconferences. We will continue NAI E/PO collaboration in FY10.

Videoconferencing technology was tested between JPL and the Barrow Arctic Science Consortium (BASC) in January 2009, in preparation for future classroom presentations by Icy Worlds scientists. Scientists and students at BASC participated in JPL’s “Life in Extreme Environments” Educator Workshop.