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"Extraterrestrial Environment"
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No thick carbon dioxide atmosphere on the rocky exoplanet TRAPPIST-1 c
Seven rocky planets orbit the nearby dwarf star TRAPPIST-1, providing a unique opportunity to search for atmospheres on small planets outside the Solar System
1
. Thanks to the recent launch of the James Webb Space Telescope (JWST), possible atmospheric constituents such as carbon dioxide (CO
2
) are now detectable
2
,
3
. Recent JWST observations of the innermost planet TRAPPIST-1 b showed that it is most probably a bare rock without any CO
2
in its atmosphere
4
. Here we report the detection of thermal emission from the dayside of TRAPPIST-1 c with the Mid-Infrared Instrument (MIRI) on JWST at 15 µm. We measure a planet-to-star flux ratio of
f
p
/
f
⁎
= 421 ± 94 parts per million (ppm), which corresponds to an inferred dayside brightness temperature of 380 ± 31 K. This high dayside temperature disfavours a thick, CO
2
-rich atmosphere on the planet. The data rule out cloud-free O
2
/CO
2
mixtures with surface pressures ranging from 10 bar (with 10 ppm CO
2
) to 0.1 bar (pure CO
2
). A Venus-analogue atmosphere with sulfuric acid clouds is also disfavoured at 2.6
σ
confidence. Thinner atmospheres or bare-rock surfaces are consistent with our measured planet-to-star flux ratio. The absence of a thick, CO
2
-rich atmosphere on TRAPPIST-1 c suggests a relatively volatile-poor formation history, with less than
9.5
−
2.3
+
7.5
Earth oceans of water. If all planets in the system formed in the same way, this would indicate a limited reservoir of volatiles for the potentially habitable planets in the system.
The detection of thermal emission from the rocky exoplanet TRAPPIST-1 c using the Mid-Infrared Instrument on the James Webb Space Telescope reveals a dayside brightness temperature that disfavours a thick, CO
2
-rich atmosphere.
Journal Article
The rogue world
Eleanor and her mother Samantha are working seperately and preparing for a journey to find the Master Concentrator when an alien spacecraft lands on Earth and throws the globe into a crisis that Eleanor works to control.
Book
The unexpected surface of asteroid (101955) Bennu
NASA’S Origins, Spectral Interpretation, Resource Identification and Security-Regolith Explorer (OSIRIS-REx) spacecraft recently arrived at the near-Earth asteroid (101955) Bennu, a primitive body that represents the objects that may have brought prebiotic molecules and volatiles such as water to Earth1. Bennu is a low-albedo B-type asteroid2 that has been linked to organic-rich hydrated carbonaceous chondrites3. Such meteorites are altered by ejection from their parent body and contaminated by atmospheric entry and terrestrial microbes. Therefore, the primary mission objective is to return a sample of Bennu to Earth that is pristine—that is, not affected by these processes4. The OSIRIS-REx spacecraft carries a sophisticated suite of instruments to characterize Bennu’s global properties, support the selection of a sampling site and document that site at a sub-centimetre scale5,6,7,8,9,10,11. Here we consider early OSIRIS-REx observations of Bennu to understand how the asteroid’s properties compare to pre-encounter expectations and to assess the prospects for sample return. The bulk composition of Bennu appears to be hydrated and volatile-rich, as expected. However, in contrast to pre-encounter modelling of Bennu’s thermal inertia12 and radar polarization ratios13—which indicated a generally smooth surface covered by centimetre-scale particles—resolved imaging reveals an unexpected surficial diversity. The albedo, texture, particle size and roughness are beyond the spacecraft design specifications. On the basis of our pre-encounter knowledge, we developed a sampling strategy to target 50-metre-diameter patches of loose regolith with grain sizes smaller than two centimetres4. We observe only a small number of apparently hazard-free regions, of the order of 5 to 20 metres in extent, the sampling of which poses a substantial challenge to mission success.
Journal Article
Where the microbes aren't
Abstract
Although a large fraction of Earth’s volume and most places beyond the planet lack life because physical and chemical conditions are too extreme, intriguing scientific questions are raised in many environments within or at the edges of life’s niche space in which active life is absent. This review explores the environments in which active microorganisms do not occur. Within the known niche space for life, uninhabited, but habitable physical spaces potentially offer opportunities for hypothesis testing, such as using them as negative control environments to investigate the influence of life on planetary processes. At the physico-chemical limits of life, questions such as whether spaces devoid of actively metabolizing or reproducing life constitute uninhabitable space or space containing vacant niches that could be occupied with appropriate adaptation are raised. We do not know the extent to which evolution has allowed life to occupy all niche space within its biochemical potential. The case of habitable extraterrestrial environments and the scientific and ethical questions that they raise is discussed.
Physical spaces where microorganisms are absent but could, in theory, persist are discussed. The mechanisms for the formation of these uninhabited but habitable spaces at macro and micro scales are discussed with examples. The use of these physical spaces in hypothesis testing is explored, especially as negative control environments to investigate geochemical and geological processes in the presence of life. The prevalence of habitable spaces on Earth and other planetary bodies is discussed.
Journal Article
Evidence of an oceanic impact and megatsunami sedimentation in Chryse Planitia, Mars
In 1976, NASA's Viking 1 Lander (V1L) was the first spacecraft to operate successfully on the Martian surface. The V1L landed near the terminus of an enormous catastrophic flood channel, Maja Valles. However, instead of the expected megaflood record, its cameras imaged a boulder-strewn surface of elusive origin. We identified a 110-km-diameter impact crater (Pohl) ~ 900 km northeast of the landing site, stratigraphically positioned (a) above catastrophic flood-eroded surfaces formed ~ 3.4 Ga during a period of northern plains oceanic inundation and (b) below the younger of two previously hypothesized megatsunami deposits. These stratigraphic relationships suggest that a marine impact likely formed the crater. Our simulated impact-generated megatsunami run-ups closely match the mapped older megatsunami deposit's margins and predict fronts reaching the V1L site. The site's location along a highland-facing lobe aligned to erosional grooves supports a megatsunami origin. Our mapping also shows that Pohl's knobby rim regionally represents a broader history of megatsunami modification involving circum-oceanic glaciation and sedimentary extrusions extending beyond the recorded megatsunami emplacement in Chryse Planitia. Our findings allow that rocks and soil salts at the landing site are of marine origin, inviting the scientific reconsideration of information gathered from the first in-situ measurements on Mars.
Journal Article
Bridging the gap between microbial limits and extremes in space: space microbial biotechnology in the next 15 years
Summary The establishment of a permanent human settlement in space is one of humanity’s ambitions. To achieve this, microorganisms will be used to carry out many functions such as recycling, food and pharmaceutical production, mining and other processes. However, the physical and chemical extremes in all locations beyond Earth exceed known growth limits of microbial life. Making microbes more tolerant of a greater range of extraterrestrial extremes will not produce organisms that can grow in unmodified extraterrestrial environments since in many of them not even liquid water can exist. However, by narrowing the gap, the engineering demands on bioindustrial processes can be reduced and greater robustness can be incorporated into the biological component. I identify and describe these required microbial biotechnological modifications and speculate on long‐term possibilities such as microbial biotechnology on Saturn’s moon Titan to support a human presence in the outer Solar System and bioprocessing of asteroids. A challenge for space microbial biotechnology in the coming decades is to narrow the microbial gap by systemically identifying the genes required to do this and incorporating them into microbial systems that can be used to carry out bioindustrial processes of interest. A challenge for space microbial biotechnology in the coming decades is to narrow the microbial gap between the growth limits of known life and conditions to be found in extraterrestrial environments.
Journal Article
Developing an alternative medium for in-space biomanufacturing
In-space biomanufacturing provides a sustainable solution to facilitate long-term, self-sufficient human habitation in extraterrestrial environments. However, its dependence on Earth-supplied feedstocks renders in-space biomanufacturing economically nonviable. Here, we develop a process termed alternative feedstock-driven in-situ biomanufacturing (AF-ISM) to alleviate dependence on Earth-based resupply of feedstocks. Specifically, we investigate three alternative feedstocks (AF)—Martian and Lunar regolith, post-consumer polyethylene terephthalate, and fecal waste—to develop an alternative medium for lycopene production using
Rhodococcus jostii
PET strain S6 (RPET S6). Our results show that RPET S6 could directly utilize regolith simulant particles as mineral replacements, while the addition of anaerobically pretreated fecal waste synergistically supported its cell growth. Additionally, lycopene production using AF under microgravity conditions achieved levels comparable to those on Earth. Furthermore, an economic analysis shows significant lycopene production cost reductions using AF-ISM versus conventional methods. Overall, this work highlights the viability of AF-ISM for in-space biomanufacturing.
Reducing reliance on Earth-supplied feedstocks is crucial for advancing in-space biomanufacturing. Here, the authors explored three alternative feedstocks – Martian and Lunar regolith, post-consumer polyethylene terephthalate, and fecal waste – to develop an alternative medium for cost-effective in-space lycopene biomanufacturing.
Journal Article
Enhanced atmospheric loss on protoplanets at the giant impact phase in the presence of oceans
Earth and Venus part company
The Mariner and Venera probes sent to Venus in the 1960s and 1970s revealed many differences between the venusian atmosphere and that on Earth. One of the hardest to account for is the preponderance of noble gases on Venus, in particular an argon-36 level 50 times higher than on Earth. A new theory tracks the cause of this difference to around 4.5 billion years ago, when Earth and Venus are thought to have grown as a result of collisions between several Mars-sized planets. Numerical simulations show that when a giant impact occurs, the presence of an ocean drastically increases the rate at which atmosphere is lost. On Earth, almost all the proto-atmosphere accrued during planet formation would have been stripped away during collisions. Venus, nearer the Sun, is unlikely to have had a major ocean, and its proto-atmosphere would have survived.
The atmospheric compositions of Venus and Earth differ significantly, with the venusian atmosphere containing about 50 times as much
36
Ar as the atmosphere on Earth
1
. The different effects of the solar wind on planet-forming materials for Earth and Venus have been proposed to account for some of this difference in atmospheric composition
2
,
3
, but the cause of the compositional difference has not yet been fully resolved. Here we propose that the absence or presence of an ocean at the surface of a protoplanet during the giant impact phase could have determined its subsequent atmospheric amount and composition. Using numerical simulations, we demonstrate that the presence of an ocean significantly enhances the loss of atmosphere during a giant impact owing to two effects: evaporation of the ocean, and lower shock impedance of the ocean compared to the ground. Protoplanets near Earth's orbit are expected to have had oceans, whereas those near Venus’ orbit are not, and we therefore suggest that remnants of the noble-gas rich proto-atmosphere survived on Venus, but not on Earth. Our proposed mechanism explains differences in the atmospheric contents of argon, krypton and xenon on Venus and Earth, but most of the neon must have escaped from both planets’ atmospheres later to yield the observed ratio of neon to argon.
Journal Article
The gymnastics of epigenomics in rice
Epigenomics is represented by the high-throughput investigations of genome-wide epigenetic alterations, which ultimately dictate genomic, transcriptomic, proteomic and metabolomic dynamism. Rice has been accepted as the global staple crop. As a result, this model crop deserves significant importance in the rapidly emerging field of plant epigenomics. A large number of recently available data reveal the immense flexibility and potential of variable epigenomic landscapes. Such epigenomic impacts and variability are determined by a number of epigenetic regulators and several crucial inheritable epialleles, respectively. This article highlights the correlation of the epigenomic landscape with growth, flowering, reproduction, non-coding RNA-mediated post-transcriptional regulation, transposon mobility and even heterosis in rice. We have also discussed the drastic epigenetic alterations which are reported in rice plants grown from seeds exposed to the extraterrestrial environment. Such abiotic conditions impose stress on the plants leading to epigenomic modifications in a genotype-specific manner. Some significant bioinformatic databases and in silico approaches have also been explained in this article. These softwares provide important interfaces for comparative epigenomics. The discussion concludes with a unified goal of developing epigenome editing to promote biological hacking of the rice epigenome. Such a cutting-edge technology if properly standardized, can integrate genomics and epigenomics together with the generation of high-yielding trait in several cultivars of rice.
Journal Article