Thriving in Space Ensuring the Future of Biological and Physical Sciences Research: A Decadal Survey for 2023-2032 (2023) / Chapter Skim
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5 Science Enabled by the Space Environment
5 Science Enabled by the Space Environment
Pages 133-157
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From page 133... ...
Chapter 5 is thus organized around a single theme that presents the priorities of science for the coming decade: Probing Phenomena Hidden by Gravity or Terrestrial Limitations: Revealing underlying biological and physical processes that cannot be quantified on Earth.
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From page 134... ...
Quests for biological science principles need to be aware of and draw from physical principles; and impactful physical science-motivated inquiries need to be aware of and leverage knowledge gained from analogy to biological systems. This is not a novel concept: the electrochemistry of today's portable batteries was inspired in form and function by the "animal chemistry" stored in twitching TABLE 5-1 Key Scientific Questions Enabled by Access to Space Over the Decade 2023–2032 Theme Key Scientific Questions Probing Phenomena • What are the mechanisms by which organisms sense and respond to physical properties of Hidden by Gravity or surroundings and to applied mechanical forces, including gravitational force?
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From page 135... ...
BPS KEY SCIENTIFIC QUESTIONS THEME 3: PROBING PHENOMENA HIDDEN BY GRAVITY OR TERRESTRIAL LIMITATIONS -- REVEALING UNDERLYING BIOLOGICAL AND PHYSICAL PROCESSES THAT CANNOT BE QUANTIFIED ON EARTH This theme can be referred to in shorthand as phenomena hidden by Earth's environment. The path to identifying the scientific principles otherwise obscured by 1 g gravity, relatively low radiation levels, and other features that define "standard conditions" of Earth-bound research is guided by the following four KSQs: • What are the mechanisms by which organisms sense and respond to physical properties of surroundings and to applied mechanical forces, including gravitational force?
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From page 136... ...
This investment recognizes the potential for significant societal impacts utilizing the space environment for the biological and physical sciences portfolio in the coming decade, aimed at • Identifying the mechanisms by which organisms sense and respond to the surrounding environment, including gravitational force; • Advancing knowledge of material structure, self-assembly, and stability of materials, including but not limited to soft/active matter, in space environments, cognizant of but distinct from the applications of that knowledge to space exploration and habitation (e.g., manufacturing in space) ; • Supporting ground-based and microgravity research on understanding the fundamental laws of systems far from equilibrium, especially those that underlie the existence of life; and • Identifying new principles of physics that can only be discovered through experiments in space, including those governing particle physics, general relativity, and quantum mechanics.
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From page 137... ...
Studies in the near-absence of gravity will enable the separation of gravitational forces from other mechanical forces necessary to understand the fundamental biological mechanisms by which gravity sensing occurs and the degree to which gravity sensors influence other mechanical responses. Because mechanosensing has a major role in guiding structural growth in biology, this understanding will have potential Earth translational
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From page 138... ...
Different gravity levels from micro- to hyper-gravity, including moon and martian levels, will enable distinction of graded responses and threshold effects of gravity and mechanical stresses whose sensation is affected by gravity, and will permit mechanical effects to be quantitated in the absence of gravitational load and of gravity sensing. This will allow a distinction to be made between the causal mechanisms of different effects, and their separate study.
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From page 139... ...
The ability to remove or change the magnitude of the gravitational vector in the space environment will allow tests of these hypotheses regarding this long-term adaptation to altered gravity and non-gravitational mechanical forces. The mechanism of gravity sensing in plants is poorly understood, and the transduction of gravity signals from the cells with amyloplasts is also only partially understood.
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From page 140... ...
The expansion of available space environments to the lunar surface and work in weightless environments such as ISS and on the way to Mars would be greatly enabled by provision of centrifuges with sufficient capacity for growing whole plants at partial gravity, as a control at 1 g, and in hypergravity. It is essential that such gene expression studies under partial gravity are expanded to include additional species of plants (beyond Arabidopsis)
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From page 141... ...
, leaving considerable scope for studies of the mechanisms of how mechanosensing works for these prokaryotic microbes in space environments, where fluid flow and consequently shear forces experienced by bacteria are expected to be altered by gravitational effects. Mechanosensing in bacteria is known to exist -- in particular, in the formation of biofilms.
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From page 142... ...
Experimentation in the low-gravity environment then achieves the idealized condition of a negligible gravitational force term and buoyancy-induced flow, thus providing an experimental capability that is nearly impossible in terrestrial laboratories (except for the reduced gravity facilities on Earth such as drop towers and aircraft flying parabolic trajectories) , and allows investigation of the influence of other factors on determining the fluid flow, chemical reactions, vibrationally and electronically excited states, and phase change processes.
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From page 143... ...
Because the interparticle forces are rather weak forces, gravitational stresses limit the size of the crystallites to tens of unit cells per side; in space environments, larger assemblies and masses suitable for fundamental experiments are possible. Moreover, many soft matter systems are microscopic, colloidal, and suspensions of particles in fluids.
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But there is much we do not know about how these passive and active soft materials interact with the space environment; these unknowns are part of stated Grand Challenges in Soft Matter Science (Mezzenga 2021)
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From page 145... ...
Experiments could quantify the scale of behaviors relative to the concentration of solutes, to understand the limits to which pure fluid analogy is sufficient with regard to "infinite dilution" assumptions. Another effect that can be clearly addressed in space environments is how the imposition of external fields -- that is, electrical, magnetic, and so on -- affects the phase change process, the orientation, motion, and separation of components and phases.
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From page 146... ...
. At pressures approaching and above the critical point of the fluid, reductions in diffusive timescales governing thermal, mass, and momentum transport occur as well as changes in solubilities that impact chemical reaction rates and rates of phase transitions (e.g., phase change heat transfer)
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From page 147... ...
New orderings of soft matter have recently been reported that have intriguing properties, such as the ability to output power rather than dissipating it. The reduced gravity of the space environment may enable the discovery of even more exotic forms of weakly bound network materials, phase transformations, and new phenomena.
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From page 148... ...
Understanding the new balance of forces and how they affect energy, heat, mass, and momentum transfer in reduced gravity is critical to controlling synthesis and processing across levels of gravitational forces and can enable creation of new multi-component materials (e.g., alloys, organic molecules/ macromolecules, including those with complex secondary structures, and composites) , and structures ranging from nanomaterials to meter-scale systems, and chemical synthesis.
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From page 149... ...
The microgravity environment provides nearly uniform hydrostatic pressure and a significant reduction in natural convection, which together enable research in high-pressure and non-equilibrium phenomena. These variations can affect thermophysical properties, reaction kinetics, and material solubility, as these are affected by the dominance of strong intermolecular forces and non-elastic multi-body collision processes.
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From page 150... ...
because of the increased probability of multi-component molecular interactions that can retard reactions because of the increased interaction between different chemical species. Non-Equilibria Phenomena in Complex Fluids Increasingly, new and emerging technologies involve phases of matter not easily classified into solid, liquid, and gas categories: "squishy" soft matter (with some examples also called complex fluids)
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From page 151... ...
These fundamental questions can be studied in several different types of matter, leveraging the unique space environment characteristics, including metallic alloys, organic soft matter, and composite materials governed by colloidal interactions. In a microgravity or partial gravity environment, it is possible to conduct clean experiments to determine how much and what type of impetus could be applied to a system at or near equilibrium to initiate a rearrangement.
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From page 152... ...
. In addition to the dark matter and dark energy problem, the standard model fails to provide explanations for several other phenomena and issues.
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From page 153... ...
Moreover, fundamental physics research in space extends beyond a quest for "new physics" and includes anticipated contributions to fundamental many-body quantum physics, predictions of phase transformations also embraced by the materials science and complex fluids communities, and methodological advances that may also advance adjacent fields such as astronomy and astrophysics. As an example of the former, transformative advances in quantum technologies have led to a plethora of new high-precision quantum devices joining the search for dark matter, dark energy, and new forces; tests of
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From page 154... ...
The enthusiastic response by the BPS research community to the request for input papers related to this decadal survey clearly demonstrates this strong interest, with a diverse array of opportunities identified for transformative fundamental physics investigations exploiting the unique space environment, away from Earth's gravity. For example, some hypothesized dark energy and dark matter fields can be screened at the surface of Earth, reducing their measurable effects by many orders of magnitude.
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From page 155... ...
As a result, atomic optical clocks in space have been proposed for a wide variety of fundamental and practical applications. Fundamental physics clock applications include tests of gravity, searches for dark matter and variation of fundamental constants, tests of Lorentz symmetry and local position invariance, measurements of gravitational waves (GWs)
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From page 156... ...
An important point to stress is that the ability to compare different clocks and clocks in different locations is required to make use of the fantastic precision and stability of optical atomic clocks -- that is, significant technological effort will also be required to implement optical time transfer between space- and ground-based optical atomic clocks. Finding 5-4: Beyond optical atomic clocks, there is a diverse array of quantum and precision measure ment technologies that will be critical to addressing space-based fundamental physics questions and as sociated applications, as outlined above.
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From page 157... ...
Thus, prudent planning and use of the space-based science and associated ground-based analogs can also anticipate surprise discoveries and innovations, prompting entirely new key questions and directions of research that are enabled specifically by access to the sub-orbital, orbital, and lunar surface environments in the coming decade. History indicates that emergent areas of space-enabled research are unlikely to be part of any existing roadmap for space exploration; the less we can predict what these future space-enabled areas are today, the more transformative they are likely to be for society in future decades.
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