Trabajadores del Hogar

Reference: Pappalardo, R. T., et al. "Science

potential from a Europa lander." Astrobiology

13.8 (2013): 740-773.

Low Velocity Impacts on Phobos. Heather D. Smith1 Pascal Lee1, 2 and Doug Hamilton3, 1Planetary Systems Branch, NASA Ames Research Center, Moffett Field, CA . E-mail: [email protected] 2. SETI Institute and Mars Institute Mountian View, CA E-mail: [email protected] 3. Department of Astronomy, Univer- sity of Maryland, College Park, MD. [email protected].

Introduction: We present evidence for low velocity impacts on Phobos resulting from material transfer from Deimos to Phobos and/ or recaputure of Phobos ejecta.

Mars’s inner moon, Phobos, is located deep in the planet’s gravity well and orbits far below the planet’s synchronous orbit. Images of the surface of Phobos, in particular from Viking Orbiters, MGS, MRO, and MEX, reveal a spectral heteogenity, rich collisional history, including fresh-looking impact craters and subdued older structures, very large impact structures (compared to the size of Phobos), such as Stickney, and much smaller ones [1, 2, 3, 4 ].

Sources of impactors colliding with Phobos include a

priori: A) Impactors from outside the martian system

(asteroids, comets, and fragments thereof); B) Im- pactors from Mars itself (ejecta from large impacts on Mars); and C) Impactors from Mars orbit, including impact ejecta launched from Deimos and ejecta launched from, and reintercepted by, Phobos. In addi- tion to individual craters on Phobos, the networks of grooves on this moon have also been attributed in part or in whole to impactors from some of these sources[5,6

7} _{as shown in Figure 1.}

Figure 1. Grooves and crater chains on Phobos. Image taken by the Viking 1 Orbiter

Method: We report the preliminary results of a sys- tematic survey of the distribution, morphology, albedo, and color characteristics of fresh impact craters and associated ejecta deposits on Phobos. Considering that the different potential impactor sources listed above are expected to display distinct dominant compositions and different characteristic impact velocity regimes, we identify specific craters on Phobos that are more likely the result of low velocity impacts by impactors

derived from Mars orbit than from any alternative

sources. Our finding supports the hypothesis that the spectrally “Redder Unit” on Phobos may be a superfi- cial veneer of accreted ejecta from Deimos, and that Phobos’s bulk might be distinct in composition from Deimos[8,9]_.

Figure 2. MRO image of Phobos showing the spectral units, orbital direction, and surface features supporting the transfer of material from Deimos to Phobos.

References: [1] Veverka, J.and Duxbury, T.C. (1977) J. Geophys Res, 82, 4213–4223. [2] Avanesov, G.A. et al. (1989) Nature, 341, 585-587. [3] Thomas, N et al. (2011) Planetary Space Sci. 59, 1281–1292. [4] Giuranna, M. et al. (2011) Planetary Space Sci. ,59, 1308-1325. [5] Weidenschilling, S.J. (1979) Nature,

282, 697-698. [6] Thomas, P. Veverka, J., Bloom, A.,

and Duxbury, T.C. (1979), J. Geophys Res, 84, 8457- 8477. [7] Asphaug, E. and Melosh H. J. (1993) Icarus,

101, 144–164. [8] Rivkin, A.S. et al. (2002) Icarus, 156, 64-75. [9] Lee, P. (2009), First International Con- ference on the Exploration of Phobos and Deimos, 5-7 Nov 2007: Summary and Recommendations.", pp 1-40.

Urban Biomining: Biological Extraction of Metals and Materials from Electronics Waste Using a Synthetic Biology Approach

Jesica Urbina-Navarrete, [email protected]

Lynn J. Rothschild, [email protected]

Abstract:

Integrated circuits (IC chips) are critical to modern technology and while relatively inexpensive on the

Earth, a supply in space must be regenerated, repurposed or repaired in situ. If an IC chip is damaged or

outdated, the processes for extracting and recycling the materials require high heat and chemical

treatments; thus, repair or replacement of IC chips is not a feasible task in space or extraterrestrial

environments where small size and low mass are required. We propose using a biological approach to

depolymerize the silicate matrix of metals- and glass-containing electronic components to release the

metals contained within. After enzymatic depolymerization of the silica, there is the additional challenge

of separating the individual elemental components. We address this issue by using rationally-designed

peptides that bind specific metals for the separation of metals from a solution at ambient temperature

and under non-toxic conditions.

Using synthetic biology tools, we have developed a recycling method for e-waste. Our innovation is to

use a recombinant version of a naturally-occurring silica-degrading enzyme to depolymerize silica, and

subsequently, to use engineered bacterial surfaces to bind and separate metals from a solution. The

bacteria with bound metals can then be used as “bio-ink” to print new circuits using a novel plasma jet

electronics printing technology. Here, we present the results from our initial studies that focus on the

specificity of metal-binding motifs for a cognate metal. The candidate motifs that show high affinity and

specificity will be engineered into bacterial surfaces for downstream applications in biologically-

mediated metal recycling.

Since the chemistry and role of Cu in metalloproteins is relatively well-characterized, we are using Cu as

a proxy to elucidate metal and biological ligand interactions with various metals in e-waste. We assess

the binding parameters of 3 representative classes of Cu-binding motifs using isothermal titration

calorimetry; 1) natural motifs found in metalloproteins, 2) consensus motifs, and 3) rationally designed

peptides that are predicted, in silico, to bind Cu. Our results indicate that naturally-occurring motifs have

relative high affinity and specificity for Cu (association constant for Cu K

~ 10

M

, Zn K

~ 10

M

) when

competing ions are present in the aqueous milieu. However, motifs developed through rational design

by applying quantum mechanical methods that take into account complexation energies of the

elemental binding partners and molecular geometry of the cognate metal, not only show high affinity

for the cognate metal (Cu K

~ 10

M

), but they show specificity and discrimination against other metal

ions that would-be competitors for the same binding sites. This is an initial proof-of-concept study that

focuses on Cu-binding; however, the overall objective of this research is to have peptides that selectively

bind many metals from e-waste and this would allow for the separation of the metals from a solution, at

ambient temperatures and under non-toxic conditions.

2017 NASA Ames Space Science & Astrobiology Jamboree

Notes

2017 NASA Ames Space Science & Astrobiology Jamboree

Notes

2017 NASA Ames Space Science & Astrobiology Jamboree

Notes

2017 NASA Ames Space Science & Astrobiology Jamboree

Notes