Astrophysics Research
The Formation of Nucleobases from the Irradiation of Purine in Astrophysical Ices
Project Participants (BAERI): C. K. Materese, M. Nuevo
Project Description
Recent experiments have shown that the irradiation of the aromatic molecules benzene (C6H6) and naphthalene (C10H8) in mixed molecular ices leads to the formation of O- and N- heterocyclic molecules. Among the class of N- heterocycles are the nucleobases– the information-bearing units of DNA and RNA. Nucleobases have been detected in meteorites, with isotopic signatures that are also consistent with an extraterrestrial origin. Three of the biologically relevant nucleobases (uracil, cytosine, and thymine) have a pyrimidine core structure while the remaining two (adenine and guanine) possess a purine core. Previous experiments have demonstrated that all of the biological nucleobases (and numerous other molecules) with a pyrimidine core structure can be produced by irradiating pyrimidine in mixed molecular ices of several compositions.
In this work, the team studied the formation of purine- based molecules, including the nucleobases adenine, and guanine from the ultraviolet (UV) irradiation of purine in ices consisting of mixtures of H2O and NH3 at low temperature. The experiments are designed to simulate the astrophysical conditions under which these species may be formed in the interstellar medium, dense molecular clouds, or on the surfaces of icy bodies of the Solar System.
Accomplishments
The UV irradiation of the experimental ice mixtures resulted in the formation of refractory residues containing functionalized purines, including the nucleobases adenine and possibly guanine, in addition to hypoxanthine, iso-guanine, amino- purines, and 2,6-diaminopurine.
Selected Publications:
The Formation of Nucleobases from the UV Irradiation of Purine in Astrophysical Ices and Comparisons with Meteorites, 79th Annual Meeting of the Meteoritical Society, held 7-12 August, 2016 in Berlin, Germany. LPI Contribution No. 1921, id.6038.
Pluto and Charon: The Non-Ice Surface Component, 47th Lunar and Planetary Science Conference, held March 21-25, 2016 at The Woodlands, Texas. LPI Contribution No. 1903, p.1700.
Ice Chemistry on Outer Solar System Bodies: Electron Radiolysis of N2-, CH4-, and CO-Containing Ices, The Astrophysical Journal, Volume 812, Issue 2, article id. 150, 9 pp. (2015).
Search for Sugars and Related Compounds in Residues Produced from the UV Irradiation of Astrophysical Ice Analogs, 78th Annual Meeting of the Meteoritical Society, held July 27-31, 2015 in Berkeley, California. LPI Contribution No. 1856, p.5142.
N- and O-heterocycles Produced from the Irradiation of Benzene and Naphthalene in H2O/NH3-containing Ices, The Astrophysical Journal, Volume 800, Issue 2, article id. 116, 8 pp. (2015).
Ring Nebula. Image courtesy of NASA
Biological Analog Science Associated with Lava Terrains (BASALT)
Project Participants BAERI: Darlene Lim
Project Description
The BASALT project is a combination science investigation of the geology and biology of Mars-like regions on the Earth and a simulation of a scientific exploration of Mars. The simulation combines “astronaut” scientists taking field samples and communicating with an “Earth-based” command center.
The GeoBioExploration will include:
- Geology: the identification and systematic sampling of Mars analog basalts with the closest textural and geochemical similarities to rock constituents directly examined on Mars
- Biology: The characterization of microbial communities within them, with special focus on sources of energy that might be plausible on Mars.
- Exploration: Concept of Operations (ConOps) development, capabilities assessment, and latency and bandwidth experiments will help to develop methodologies for managing time-delayed communications and data transmission constraints critical to lowering risks and mitigating mission complexities associated with future human scientific exploration of Mars. For this the team will employ mobile science platforms, extravehicular informatics, display technologies, communication & navigation packages, remote sensing, advanced science mission planning tools, and scientifically-relevant instrument packages.
Accomplishments
- The BASALT team conducted its first scientific fieldwork under simulated Mars mission constraints this past summer (Twitter feed here). The goal was to identify which human-robotic Concept of Operations and supporting capabilities enable science return and discovery. Additional fieldwork is planned for sites in Hawaii;
- The program aims to assess the habitability of past and present Martian environments by focusing on the extant organisms within diverse basaltic terrains, acknowledging environmental differences between both planets, and linking these communities to their intrinsic geochemical conditions;
- In the laboratory, DNA will be extracted for 16S rRNA gene-based phylogeny. Primers targeting metabolic groups of interest will elucidate functional capabilities. These methods proved robust for prokaryotic community analysis in volcanic rocks.
Selected Publications:
Diverse Eruptions at ~2,200 Years B.P. on the Great Rift, Idaho: Inferences for Magma Dynamics Along Volcanic Rift Zones, 47th Lunar and Planetary Science Conference, held March 21-25, 2016 at The Woodlands, Texas. LPI Contribution No. 1903, p.2841.
Reconstructing Phreatic Blasts from Ballistic Block Fields at Kings Bowl, Idaho, 47th Lunar and Planetary Science Conference, held March 21-25, 2016 at The Woodlands, Texas. LPI Contribution No. 1903, p.2514.
Basalt Lava Flow Texture Identification at Different Data Resolutions, 47th Lunar and Planetary Science Conference, held March 21-25, 2016 at The Woodlands, Texas. LPI Contribution No. 1903, p.2403.
FINESSE Spaceward Bound — Teacher Engagement in NASA Science and Exploration Field Research, 47th Lunar and Planetary Science Conference, held March 21-25, 2016 at The Woodlands, Texas. LPI Contribution No. 1903, p.2295.
Pre-Mission Input Requirements to Enable Successful Sample Collection by a Remote Field/EVA Team, 47th Lunar and Planetary Science Conference, held March 21-25, 2016 at The Woodlands, Texas. LPI Contribution No. 1903, p.1300.
Europa. Image courtesy of NASA
NASA K2 Mission
Project Participants BAERI: Thomas Barclay, Geert Barentsen
Project Description
The Kepler spacecraft launched with four reaction wheels, three used to help steer the spacecraft and one spare. By May 2013, two of the wheels had failed, making it impossible to continue pointing the spacecraft at a single star-field. Engineers worked out a scheme where the photon pressure from the sun would stabilize one axis of the spacecraft while the remaining two reaction wheels stabilized the other two axes. This enables the spacecraft to observe a series of star-fields along the ecliptic for a period of 80 days each. The science goals of the K2 mission include: time variable observations of Solar System objects, extrasolar planets, star clusters, and supernovae.
Accomplishments
In just 2 years, K2 has already extended the legacy of the Kepler mission by making a number of exciting discoveries:
- In the field of exoplanets, K2 has discovered small super-Earth-size planets orbiting in the habitable zone of nearby cool M dwarf stars;
- K2 has revealed different classes of variability in young stars as well as a surprising variety of pulsations in the Pleiades “Seven Sisters” stars;
- K2 is providing insight into the progenitors of Type Ia supernovae;
- K2 is observing planets and asteroids in our solar system; and
- K2 is about to begin a gravitational microlensing experiment by observing stars located in the Galactic bulge.
With approximately two more years of observations expected from K2, many more exciting discoveries are anticipated.
Selected Publications:
Planetary Candidates Observed by Kepler. VII. The First Fully Uniform Catalog Based on the Entire 48-month Data Set (Q1–Q17 DR24), The Astrophysical Journal Supplement Series, Volume 224, Issue 1, article id. 12, 27 pp. (2016).
The K2 Ecliptic Plane Input Catalog (EPIC) and Stellar Classifications of 138,600 Targets in Campaigns 1-8, The Astrophysical Journal Supplement Series, Volume 224, Issue 1, article id. 2, 17 pp. (2016).
K2 Rotation Periods for Low-mass Hyads and the Implications for Gyrochronology, The Astrophysical Journal, Volume 822, Issue 1, article id. 47, 18 pp. (2016).
Hot super-Earths stripped by their host stars, Nature Communications, Volume 7, id. 11201 (2016).
The Frequency of Giant Impacts on Earth-like Worlds, The Astrophysical Journal, Volume 821, Issue 2, article id. 126, 13 pp. (2016).
Horse head Nebula (infrared). Image courtesy of Wikipedia
Pure and N-substituted Small Cyclic Hydrocarbon Synthesis in the Gas Phase
Project Participants (BAERI): Partha P. Bera
Project Description
Several polyatomic molecules have been identified in various astrophysical environments. There are various models to explain their synthesis in such exotic conditions. Barrier-less ion-molecule interactions play a major role (ions provide electrostatic steering force) in guiding molecules towards each other and initiating reactions. The team studies these condensation pathways to determine whether they are a viable means of forming large pure and nitrogen-containing hydrocarbon chains, stacks, and cyclic compounds.
Accomplishments
- The team found that the molecular building blocks of polycyclic aromatic hydrocarbons such as phenyl cations can form very easily by the combination of starting with smaller hydrocarbons followed by hydrogen loss;
- The team explored how nitrogen atoms are incorporated into the carbon ring during growth, and specifically, in conjunction with ion-mobility experiments, the mechanisms by which the synthesis of pyrimidine is feasible in the atmosphere of Titan;
- These investigations were performed using accurate ab initio quantum chemical methods together with large correlation consistent basis sets; and
- They found that a series of hydrocarbons with a specific stoichiometric composition prefer to form cyclic molecules rather than chains.
Selected Publications:
Mechanisms, for the Formation of Thymine Under Astrophysical Conditions and Implications for the Origin of Life, Chem. Phys., 144, 144308 (2016)
Characterization of the Azirinyl Cation and Its Isomers, J. Phys. Chem.A, 120, 1275 (2016)
Low Temperature Formation of Nitrogen-substituted Polycyclic Aromatic Hydrocarbons (PANHs)- Barrierless Routes to Dihydro(iso)quinolones, The Astrophysical Journal, Volume 815, Issue 2, article id. 115, 13 pp. (2015).
Image courtesy of Scott S. Hughes
Ionizing Radiation on the Surface of Europa
Project Participants (BAERI): Luis Teodoro, NASA Ames: A. F. Davila, C. P. McKay, R. C. Elphic
Project Description
Jupiter’s moon, Europa, has a subsurface ocean under its icy shell which is a possible abode for life. The Chaos regions on the planet might provide direct access to materials from shallow pockets of liquid water within the ice shell. These are ideal locations to search for possible evidence of life, such as organic biomarkers. The best environment for such evidence would be the orbital “upstream” hemisphere, shielded from much of Jupiter’s radiation belt flux, but where galactic cosmic rays (GCRs) still interact with surface materials.
GCRs that strike Europa’s surface produce ionizing radiation in the form of high-energy electrons, protons, gamma rays, neutrons and muons. The effects of ionizing radiation in matter always involve the destruction of chemical bonds and the creation of free radicals. Both can destroy organic biomarkers over time.
Using ionizing radiation transport codes, the project recreated the most favorable radiation environment on the surface of Europa, and evaluated its possible effects on organic biomarkers within the shallow ice-shell.
Accomplishments
- The team performed a full Monte-Carlo simulation of the reactions induced by the Galactic cosmic rays hitting Europa’s surface using the Planet- cosmic code;
- Preliminary results show that the flux of ionizing radiation as a function of depth in Europa’s ice shell is similar in magnitude to that estimated for the surface on Mars for pure ice;
- Results indicate that dormant microorganisms within the top 1 meter of regolith of the most favorable Europan hemisphere would likely be killed in less than 150,000 years due to cumulative radiation damage;
- The preliminary results also indicate that even in the best-case Europan radiation environment, created by galactic cosmic rays alone, biomolecules would be heavily damaged quickly. Complex organic molecules, including biomarkers, could become heavily processed in the top 1 meter in time scales >1 million years, and smaller organic molecules such as amino acids could be severely damaged in time scales <100 million years; and
- In conclusion, the team determined that a better constraint on the surface age of Chaos regions on Europa might be critical to the success of such missions. If surface ice deposits are fresh and young, biomarkers may be preserved.
Selected Publications:
Ionizing Radiation on the Surface of Europa: Implications for the Search for Evidence of Life, 47th Lunar and Planetary Science Conference, held March 21-25, 2016 at The Woodlands, Texas. LPI Contribution No. 1903, p.2601.
Recurring Slope Lineae on Mars are Not Fed by Subsurface Water, 47th Lunar and Planetary Science Conference, held March 21-25, 2016 at The Woodlands, Texas. LPI Contribution No. 1903, p.2813.
Molecular Diffusion of H2O in Lunar Regolith During Lunar Resources Prospector Mission Sample Acquisition, Annual Meeting of the Lunar Exploration Analysis Group, held 20-22 October, 2015 in Columbia, Maryland. LPI Contribution No. 1863, p.2058.
