Month: July 2021

On its own, a black hole is remarkably easy to describe. The only observable properties of a black hole are its mass, its electrical charge (usually zero), and its rotation or spin. It doesn’t matter how a black hole forms. Ultimately, all black holes have the same general structure. Which is strange when you think about it. Throw enough iron and stone together and you will have a planet. Throw hydrogen and helium together and you can make a star. But you could throw clippings of grass, chewing gum, and old Harry Potter books together and you’d end up with the same kind of black hole that you would get if you just used pure hydrogen.

This strange behavior of black holes is known as the no-hair theorem and relates to what is known as the information paradox. In short, since everything in the universe can be described by a certain amount of information and objects cannot simply disappear, the total amount of information in the universe should be constant. But when you throw a chair into a black hole it only increases the mass and spin of the black hole. All information about the color of the chair, whether made of wood or steel, large or small, is lost. Where did this information go?

A black hole appears to remove information from objects. Recognition: [email protected] – Gravitation @ University of Aveiro

A solution to this information paradox could be possible thanks to Stephen Hawking. As early as 1974 he showed that the event horizon of a black hole may not be absolute. Because of the quantum uncertainty, black holes should emit a tiny amount of light, known today as Hawking radiation. Hawking radiation has never been observed, but if it does exist, the information lost when objects enter a black hole could be transported out of the black hole via this light. Thus, the information is not really lost.

If the Hawking radiation is real, it also means that black holes obey the laws of thermodynamics. It’s an idea first suggested by Jacob Bekenstein. When black holes emit light, they must be at a thermal temperature. Based on Bekenstein’s idea, several physicists have shown that there are a number of laws governing black holes known as black hole thermodynamics.

Since you are reading this article, you are probably familiar with the second law of thermodynamics, which states that the entropy of any system must increase. Because of this, a cup of hot coffee will cool down over time and heat the room slightly until the coffee and the room are all the same temperature. You never see a cold cup of coffee warming up spontaneously and at the same time cooling the room slightly. Another way of formulating the second law is that heat flows from a hot object to cooler objects around it.

Gravitational wave data shows an increase in black hole area. Photo credit: Isi, Maximiliano, et al

For black holes, the second law of thermodynamics applies to the area of ​​the event horizon of a black hole. The Hawking temperature of a black hole is related to this area. The bigger the black hole, the lower its Hawking temperature. The second law of thermodynamics of black holes says that for every merging of black holes, the entropy must increase. This means that the surface area of ​​the resulting black hole must be larger than the surface area of ​​the two original black holes combined. This is known as the Hawking area theorem.

All of this, of course, is a bunch of mathematical theory. It is what we expect given our understanding of physics, but proving it is a different matter. Now a study in Physical Review Letters has shown us that this is true.[^1] The team examined the very first observation of two merging black holes. The event is known today as GW150914 and was a merger of a black hole with 29 solar masses and one 36 solar masses. Using a new method of analyzing the gravitational waves they generated, the team was able to calculate the event horizon surfaces for the original black holes. When they compared it to the surface of the last black hole with 62 solar masses, they found that the total area has increased.

The results have a 97% confidence level, which is good but not strong enough to be clinch proof. But this method can be applied to other black hole mergers, and it is the first real evidence that black hole thermodynamics is more than just a theory.

Reference: Isi, Maximiliano, et al. “Testing the Black Hole Area Law with GW150914.” Physical Review Letters 127.1 (2021): 011103.

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We may need to add a new category: Totalitarian Delusions of Grandeur

You vil live in your pod, eat slurry, and like it! Nothing like modeling “six dimensions of human need satisfaction”.

This paper says all the quiet parts out loud.

Author links open overlay panel JefimVogela Julia K.Steinbergerba Daniel W.O’Neilla William F.Lambca JayaKrishnakumarda Sustainability Research Institute, School of Earth and Environment, University of Leeds, UKb Institute of Geography and Sustainability, Faculty of Geosciences and Environment, University of Lausanne, Switzerlandc Mercator Research Institute on Global Commons and Climate Change, Berlin, Germanyd Institute of Economics and Econometrics, Geneva School of Economics and Management, University of Geneva, Switzerland

Received 26 July 2020, Revised 27 April 2021, Accepted 7 May 2021, Available online 29 June 2021.

https://doi.org/10.1016/j.gloenvcha.2021.102287

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Under a Creative Commons license open access

Highlights

• No country sufficiently meets human needs within sustainable levels of energy use.
• Need satisfaction and associated energy requirements depend on socio-economic setups.
• Public services are linked to higher need satisfaction and lower energy requirements.
• Economic growth is linked to lower need satisfaction and higher energy requirements.
• Countries with good socio-economic setups could likely meet needs at low energy use.

Abstract

Meeting human needs at sustainable levels of energy use is fundamental for avoiding catastrophic climate change and securing the well-being of all people. In the current political-economic regime, no country does so. Here, we assess which socio-economic conditions might enable societies to satisfy human needs at low energy use, to reconcile human well-being with climate mitigation.

Using a novel analytical framework alongside a novel multivariate regression-based moderation approach and data for 106 countries, we analyse how the relationship between energy use and six dimensions of human need satisfaction varies with a wide range of socio-economic factors relevant to the provisioning of goods and services (‘provisioning factors’). We find that factors such as public service quality, income equality, democracy, and electricity access are associated with higher need satisfaction and lower energy requirements (‘beneficial provisioning factors’). Conversely, extractivism and economic growth beyond moderate levels of affluence are associated with lower need satisfaction and greater energy requirements (‘detrimental provisioning factors’). Our results suggest that improving beneficial provisioning factors and abandoning detrimental ones could enable countries to provide sufficient need satisfaction at much lower, ecologically sustainable levels of energy use.

However, as key pillars of the required changes in provisioning run contrary to the dominant political-economic regime, a broader transformation of the economic system may be required to prioritise, and organise provisioning for, the satisfaction of human needs at low energy use.

Graphical abstract

Keywords

Sustainability Well-being Human needs Energy use Social provisioning Human development

1. Introduction

Limiting global warming to 1.5 °C without relying on negative emissions technologies requires not only rapid decarbonisation of global energy systems but also deep reductions in global energy use (Grubler et al., 2018, IPCC, 2018). At the same time, billions of people around the globe are still deprived of basic needs, and current routes to sufficient need satisfaction all seem to involve highly unsustainable levels of resource use (O’Neill et al., 2018). The way societies design their economies thus seems misaligned with the twin goals of meeting everyone’s needs and remaining within planetary boundaries (O’Neill et al., 2018, Raworth, 2017). This study addresses this issue by empirically assessing how the relationship between energy use and need satisfaction varies with the configurations of key socio-economic factors, and what configurations of these factors might enable societies to meet human needs within sustainable levels of energy use.

While these questions are poorly understood and empirically understudied (Brand Correa and Steinberger, 2017, Lamb and Steinberger, 2017, O’Neill et al., 2018, Roberts et al., 2020), the corner pieces of the research puzzle are largely in place. We roughly know the maximum level of final energy use (~27 GJ/cap) that can be globally rendered ecologically ‘sustainable’ (compatible with avoiding 1.5 °C of global warming without relying on negative emissions technologies) with deep transformations of energy systems (Grubler et al., 2018, IPCC, 2018). We understand what defines and characterises human needs, and what levels of which goods, services and conditions generally satisfy these needs (Doyal and Gough, 1991, Max-Neef, 1991, Millward-Hopkins et al., 2020, Rao and Min, 2018a).

We also know the basic characteristics of the cross-country relationship between energy use and a wide range of needs satisfaction indicators, including life expectancy, mortality, nourishment, education, and access to sanitation and drinking water (Burke, 2020, Lambert et al., 2014, Mazur and Rosa, 1974, Rao et al., 2014, Steinberger and Roberts, 2010). While at low levels of energy use, these need satisfaction indicators strongly improve with increasing energy use, they generally saturate at internationally moderate levels of energy use (ibid.). Beyond that saturation level, need satisfaction improvements with additional energy use quickly diminish, reflecting the satiability of needs (Doyal and Gough, 1991).

How much energy use is required to provide sufficient need satisfaction is only scarcely researched, and the few existing estimates are broadly scattered (Rao et al., 2019). Empirical cross-national estimates include 25–40 GJ/cap primary energy use for life expectancy and literacy (Steinberger and Roberts, 2010), or 22–58 GJ/cap final energy use for life expectancy and composite basic needs access (Lamb and Rao, 2015). Empirically-driven bottom-up model studies estimate the final energy footprints of sufficient need satisfaction in India, South Africa and Brazil to range between 12 and 25 GJ/cap (Rao et al., 2019), based on Rao and Min’s (2018a) definition of ‘Decent Living Standards’ that meet human needs. Global bottom-up modelling studies involving stronger assumptions of technological efficiency and equity, respectively, suggest that by 2050, Decent Living Standards could be internationally provided with 27 GJ/cap (Grubler et al., 2018) or even just 13–18 GJ/cap final energy use (Millward-Hopkins et al., 2020). Together, these studies demonstrate that meeting everyone’s needs at sustainable levels of energy use is theoretically feasible with known technology.

What remains poorly understood, however, is how the relationship between human need satisfaction and energy use (or biophysical resource use) varies with different socio-economic factors (Lamb and Steinberger, 2017, O’Neill et al., 2018, Steinberger et al., 2020). A small number of studies offer initial insights. The environmental efficiency of life satisfaction, presented as a measure of sustainability, follows an inverted-U-shape with Gross Domestic Product (GDP), increases with trust, and decreases with income inequality (Knight and Rosa, 2011). The carbon or environmental intensities of life expectancy, understood as measures of unsustainability, increase with income inequality (Jorgenson, 2015), urbanisation (McGee et al., 2017) and world society integration (Givens, 2017). They furthermore follow a U-shape with GDP internationally (Dietz et al., 2012), though increasing with GDP in all regions but Africa (Jorgenson, 2014, Jorgenson and Givens, 2015), and show asymmetric relationships with economic growth and recession in ‘developed’ vs. ‘less developed’ countries (Greiner and McGee, 2020). Their associations with uneven trade integration and exchange vary with levels of development (Givens, 2018). Democracy is not significantly correlated with the environmental efficiency of life satisfaction (Knight and Rosa, 2011) nor with the energy intensity of life expectancy (Mayer, 2017). All of these studies either combine need satisfaction outcomes from societal activity and biophysical means to societal activity into a ratio metric, or analyse residuals from their regression. Hence, they do not specify how these socio-economic factors interact with the highly non-linear relationship between need satisfaction and biophysical resource use, or with the ability of countries to reach targets simultaneously for need satisfaction and energy (or resource) use.

The socio-economic conditions for satisfying human needs at low energy use have been highlighted as crucial areas of research (Brand Correa and Steinberger, 2017, Lamb and Steinberger, 2017, O’Neill et al., 2018, Roberts et al., 2020), but remain virtually unstudied. While the theoretical understanding of this issue has seen important advances (Bohnenberger, 2020, Hickel, 2020, Stratford, 2020, Stratford and O’Neill, 2020, Gough, 2017, Kallis et al., 2020, Parrique, 2019), empirical studies are almost entirely absent. Lamb, 2016a, Lamb, 2016b qualitatively discusses socio-economic factors in enabling low-energy (or low-carbon) development, but only for a small number of countries. Furthermore, Lamb et al. (2014) explore the cross-country relationship between life expectancy and carbon emissions in light of socio-economic drivers of emissions, but do not quantitatively assess how life expectancy is related to carbon emissions nor to socio-economic emissions drivers. Quantitative empirical cross-country analyses of the issue thus remain entirely absent.

We address these research gaps by making three contributions. First, we develop a novel analytical approach for empirically assessing the role of socio-economic factors as intermediaries moderating the relationship between energy use (as a means) and need satisfaction (as an end), thus analytically separating means, ends and intermediaries (Fig. 1). For this purpose, we adapt and operationalise a novel analytical framework proposed by O’Neill et al. (2018) which centres on provisioning systems as intermediaries between biophysical resource use and human well-being (Fig. 1A). Second, we apply this approach and framework for the first time, using data for 19 indicators and 106 countries to empirically analyse how the relationships between energy use and six dimensions of human need satisfaction vary with a range of political, economic, geographic and infrastructural ‘provisioning factors’ (Fig. 1B). Third, we assess which socio-economic conditions (i.e. which configurations of provisioning factors) might enable countries to provide sufficient need satisfaction within sustainable levels of energy use. Specifically, we address the following research questions:1)

What levels of energy use are associated with sufficient need satisfaction in the current international provisioning regime?2)

How does the relationship between energy use and human need satisfaction vary with the configurations of different provisioning factors?3)

Which configurations of provisioning factors are associated with socio-ecologically beneficial performance (higher achievements in, and lower energy requirements of, human need satisfaction), and which ones are associated with socio-ecologically detrimental performance (lower achievements in, and greater energy requirements of, need satisfaction)?4)

To what extent could countries with beneficial configurations of key provisioning factors achieve sufficient need satisfaction within sustainable levels of energy use?

The remainder of this article is structured as follows. We introduce our analytical framework and outline our analytical approach in Section 2. We describe our variables and data in Section 3, and detail our methods in Section 4. We present the results of our analysis in Section 5, and discuss them in Section 6. We summarise and conclude our analysis in Section 7.

2. Analytical framework and approach

Building on the work of O’Neill et al. (2018), our analytical framework (Fig. 1A) conceptualises the provisioning of human needs satisfaction in an Ends–Means spectrum (Daly, 1973). Our framework considers energy use as a means, and need satisfaction as an end, with provisioning factors as intermediaries that moderate the relationship between means and ends. We thus operationalise O’Neill et al.’s (2018) framework by reducing the sphere of biophysical resource use to energy use (for analytical focus), and reducing the sphere of human well-being to human need satisfaction (for analytical coherence). Our operationalisation of human need satisfaction follows Doyal and Gough’s (1991) Theory of Human Need, reflecting a eudaimonic understanding of well-being as enabled by the satisfaction of human needs, which can be evaluated based on objective measures (Brand Correa and Steinberger, 2017, Lamb and Steinberger, 2017).

The main advancement of our framework consists in operationalising the concept of provisioning systems (Brand Correa and Steinberger, 2017, Fanning et al., 2020, Lamb and Steinberger, 2017, O’Neill et al., 2018) by introducing the concept of ‘provisioning factors’.

Provisioning factors comprise all factors that characterise any element realising, or any aspect influencing, the provisioning of goods and services. This includes economic, political, institutional, infrastructural, geographic, technical, cultural and historical characteristics of provisioning systems (or the provisioning process), spanning the spheres of extraction, production, distribution, consumption and disposal. In other words, provisioning factors encompass all factors that affect how energy and resources are used to meet human needs (and other ends). For example, it matters whether provisioning caters to consumers with equal or unequal purchasing power, whether it occurs in an urban or rural context, in a growing or shrinking economy, whether electricity is available, and what transport infrastructure is in place. Provisioning factors are intermediaries that moderate the relationship between energy use and need satisfaction. Whereas provisioning systems are broad conceptual constructs that are difficult to measure, provisioning factors are tangible and measureable, and as such operational: provisioning factors characterise provisioning systems (or the provisioning process).

While interactions between energy use, provisioning factors and social outcomes may in principle go in all directions (Fanning et al., 2020, O’Neill et al., 2018), our focus here is on the role of provisioning factors for countries’ socio-ecological performance, i.e. their achievements in, and energy requirements of, human need satisfaction (Fig. 1A). We use regression-based moderation analysis (Section 4.2) to assess how the relationship between energy use and need satisfaction varies with different provisioning factors, and subsequently model that relationship for different configurations of each provisioning factor (Fig. 1B). We further estimate how multiple provisioning factors jointly interact with the relationship between need satisfaction and energy use, using multivariate regression analysis (Section 4.3). While these are established statistical techniques, the way we apply them to our analytical framework and research questions is novel. Our approach allows us to coherently assess and compare the interactions of a broad range of provisioning factors, not just with need satisfaction or its ratio with energy use, but with the relationship between need satisfaction and energy use, across the international spectrum.

The variables assessed in our analytic framework (listed in Fig. 1A and detailed in Table 1, Table 2) capture key dimensions of human need, key categories of provisioning (state provision, political economy, physical infrastructure and geography) as well as total final energy use. Based on our understanding of human need theory (Doyal and Gough, 1991, Max-Neef, 1991) and provisioning systems (Brand Correa and Steinberger, 2017, Gough, 2019, O’Neill et al., 2018, Fanning et al., 2020), we analyse electricity access, democratic quality and income equality as provisioning factors (intermediaries) rather than as indicators of human need satisfaction (outcomes).

Table 1. Human need satisfaction variables used in the analysis.

Variable name	Description and [units]	Sufficiency threshold	Indicator source
Healthy life expectancy	Average healthy life expectancy at birth [years]	65 years	IHME GBD
Sufficient nourishment	Percentage of population meeting dietary energy requirements [%], calculated as the reverse of Prevalence of undernoursihment, rescaled onto a scale from 0 to 100%	95%	WB WDI 2020
Drinking water access	Percentage of population with access to improved water source [%]	95%	WB WDI 2017
Safe sanitation access	Percentage of population with access to improved sanitation facilities [%]	95%	WB WDI 2017
Basic education	Education index [score]	score of 75	UNDP HDR
Minimum income	Absence of income shortfall below $3.20/day [%], calculated as the reverse of the Poverty gap at $3.20 a day (2011 PPP)	95%	WB WDI 2020

Saturation transformations are applied to all need satisfaction variables (see Supplementary Materials Section C.4.2). Indicator sources are: the Global Burden of Disease Study (IHME GBD; Institute for Health Metrics and Evaluation, 2017), the World Development Indicators (WB WDI; World Bank, 2017, World Bank, 2020), and the Human Development Report 2013 (UNDP HDR; UNDP, 2013).

Table 2. Provisioning factor variables used in the analysis.

Variable name	Description and [units]	Trans-formation applied	Indicator source
Electricity access	Percentage of population with access to electricity [%]	Saturation	WB WDI 2017
Access to clean fuels	Percentage of population with access to non-solid fuels [%]	Saturation	WB WDI 2017
Trade & transport infrastructure	Quality of trade and transport-related infrastructure [score], component of the Logistics performance index	Identity	WB WDI 2017
Urban population	Percentage of population living in urban areas [%]	Identity	WB WDI 2017
Public service quality	Quality of public services, civil service, and policy implementation [score], calculated as Government effectiveness, rescaled onto a scale from 1 to 6	Identity	WB WGI
Public health coverage	Percentage of total health expenditure covered by government, non-governmental organisations, and social health insurance funds [%]	Identity	WB WDI 2017
Democratic quality	Ability to participate in selecting government, freedom of expression and association, free media [score], calculated as Voice and accountability, rescaled onto a scale from 1 to 6	Saturation	WB WGI
Income equality	Equality in household disposable income [score], calculated as the reverse of the Gini index	Saturation	SWIID
Economic growth	3-year (2010–2012) average percentage annual growth rate of GDP per capita in constant 2011 $ PPP [%], calculated based on Gujarati, 1995, pp. 169–171	Identity	WB WDI 2017
Extractivism	Share of total value generation obtained from total natural resource rents [% of GDP]	Logarithmic	WB WDI 2017
Foreign direct investments	Share of foreign direct investments (net inflow) in total value generation [% of GDP]	Logarithmic	WB WDI 2017
Trade penetration	Share of total value generation that is traded [% of GDP], calculated as Importvalue+Exportvalue	Identity	WB WDI 2020

Indicator sources are: the World Development Indicators (WB WDI; World Bank, 2017, World Bank, 2020), the Worldwide Governance Indicators (WB WGI; World Bank, 2018, Kaufmann et al., 2011), and the Standardized World Income Inequality Database v6.2 (SWIID; Solt, 2020).

Read the full paper here.

And don’t miss the following section, emphasis mine:

6.4. Paradigmatic provisioning factors: Economic growth and (in)equality

Our findings challenge the influential claim that economic growth is beneficial to human well-being. In fact, our results suggest that at moderate or high levels of energy use, economic growth is associated with socio-ecologically detrimental performance (lower achievements in, and greater energy requirements of, need satisfaction). Given the close coupling between economic activity and energy use (Steinberger et al., 2020), these findings imply that economic growth beyond moderate levels of affluence is socio-ecologically detrimental. At low levels of energy use (currently corresponding to low levels of affluence), economic growth exhibits no significant association with need satisfaction. Joint analysis with other provisioning factors corroborates the adverse outcomes associated with economic growth (Supplementary materials Table B.2). These findings run contrary to the near-universal policy goal of fostering economic growth. Due to our novel approach of analysing economic growth as a provisioning factor, our results analytically integrate multiple critiques of growth: the social limits and detriments of growth (Hirsch, 1976, Kallis, 2019, Mishan and Mishan, 1967, O’Neill, 2015); the ecological unsustainability of growth (Dietz and O’Neill, 2013, Jackson, 2017, Kallis, 2018, Kallis, 2019); and the incompatibility of growth with limiting global warming to 1.5 °C (Antonakakis et al., 2017, D’Alessandro et al., 2020, Haberl et al., 2020, Hickel and Kallis, 2020). Abandoning the pursuit of economic growth beyond moderate levels of affluence thus appears ecologically necessary and socially desirable. Rendering a non-growing economy socially sustainable will require a fundamental political-economic transformation to remove structural and institutional growth dependencies (Hickel, 2020, Hinton, 2020, Kallis et al., 2020, Parrique, 2019, Stratford, 2020, Stratford and O’Neill, 2020).

Our findings also add new perspectives to the controversial debate on how income (in)equality relates to energy use and carbon emissions (Grunewald et al., 2017, Jorgenson et al., 2016, Oswald et al., 2021, Rao and Min, 2018b). By assessing income equality as a provisioning factor, our analysis integrates previous findings related to both biophysical resource use and social outcomes. The positive association we find between income equality and socio-ecological performance supports claims that improving income equality is compatible with rapid climate mitigation (D’Alessandro et al., 2020, Oswald et al., 2021, Rao and Min, 2018b), beneficial for social outcomes (Wilkinson and Pickett, 2010) and favourable (Jorgenson, 2015, Knight and Rosa, 2011, Oswald et al., 2021) or even required (Gough, 2017) for reconciling human well-being with ecological sustainability. These findings are particularly important as inequality is on the rise in many countries (Piketty and Saez, 2014), and as efforts to limit resource use could lead to escalating inequality through intensified economic rent extraction (Stratford, 2020). Taken together, these analyses provide a strong case for redistributive policies that establish both minimum and maximum income and/or consumption levels (Alexander, 2014, Fuchs and Di Giulio, 2016, Gough, 2020).

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Related

Since 1971, when the Mariner 9 probe surveyed the surface of Mars, scientists have theorized that there may be ice beneath the surface beneath the southern polar ice cap on Mars. In 2004, ESA’s Mars Express orbiter further confirmed this theory when its Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument detected something at a depth of 3.7 km (2.3 miles) below the surface, that looked like water ice.

These results were very encouraging as they suggested that there might still be sources of liquid water on Mars where life could survive. Unfortunately, after reviewing the MARSIS data, a team of researchers led by Arizona State University (ASU) suggested an alternate explanation. As they showed in a recent study, the radar reflections could be the result of clays, metal-containing minerals, or salty ice beneath the surface.

The study, which recently appeared in the Geophysical Research Letters, was led by Carver J. Bierson – a postdoctoral fellow at ASU’s School of Earth and Space Exploration (SESE). He was supported by Professor Slawek Tulaczyk of UC Santa Cruz (UCSC), ASU research fellow Samuel Courville, and Nathaniel Putzig – a senior scientist at the Planetary Science Institute (PSI) – in geo and planetary sciences.

A view of the southern polar plane of Mars with the area scanned by MARSIS highlighted. Photo credit: USGS Astrogeology Science Center / ASU / INAF

The MARSIS instrument works by directing a ground penetrating radar beam onto the Martian surface and then measuring the reflected echo. An underground zone of liquid water has completely different electrical properties than surrounding ice or rock and will reflect very strongly. This technique enabled the Mars Express to create an underground map of Mars to a depth of 3 miles.

In 2018, an analysis of subsurface radar reflections by a team of Italian researchers focused primarily on electrical permittivity, which controls the speed of radio waves within a material. The denser the material in question (water, ice, rock, etc.), the slower the waves propagate and the power of the reflected waves is also affected. Due to its brightness, this bright radar reflection was interpreted as a large patch of liquid, salty water.

However, the radar reflection may be bright due to a large contrast in either dielectric permittivity or electrical conductivity. As Putzig explains in a PSI press release:

“It is not necessary to conjure up liquid water at the base of the polar cap to explain the results of the MARSIS observations. Alternatives are clays, some metallic minerals, and salty ice. Because water – especially in liquid form – is so important to the maintenance of life, it is of the utmost importance for astrobiological studies to find out where it could be on Mars today or in the past. It is critical to the scientific process to ensure that we fully consider other options for reported evidence of liquid water. “

Artist’s impression of water beneath the surface of Mars. If there were indeed underground aquifers, the effects on human exploration and the eventual settlement of the Red Planet would be far-reaching. Photo credit: ESA

In contrast, the new research focused on electrical conductivity, where conductivity contrasts between materials could also explain the bright radar reflection. “Our team wanted to take a step back and ask if there were any other materials besides liquid water that could be causing these bright reflections,” said Bierson. “Salt ice or conductive minerals at the base of the ice sheet are less noticeable, but they correspond more to the extremely cold temperatures at the Martian poles.”

Dielectric constant or electrical conductivity are related, but most previous evaluations of subsurface radar reflections have chosen to focus on the former and neglect the latter. Attributing them to salty water supplies was hardly unreasonable and may have been little influenced by wishful thinking. Scientists have known for decades that about 4 billion years ago there was running water and possibly microbial life on the surface of Mars.

Since then, various pieces of evidence have surfaced suggesting that much of this water retreated underground as the Martian climate underwent a massive transition and became the extremely cold, arid, and highly irradiated environment we see there today. Knowing that there are abundant water supplies underground, especially in the mid-latitudes, would also be a boon for future manned missions to the Red Planet. Said Putzig:

“This decision led previous workers to conclude that liquid water – likely very salty to be liquid at the temperatures and pressures expected 1.5 kilometers below the surface of Mars’ south polar ice cap – the most reasonable explanation for that The reflectivity of the radar is high. However, the work presented in this paper shows that conductivity can be an important factor for some materials, and therefore such materials offer a viable alternative explanation for the data. “

Radar detection of water under the south pole of Mars. Photo credit: ESA / NASA / JPL / ASI / Univ. Rome

This may seem a little daunting to those who believe we will find life on Mars, but it is important to remember that this research is just exploring all possibilities. Assuming there is simply more ice beneath the south polar layered deposits, this is still good news for those who hope that astronauts will explore Mars’ South Pole in the years to come (or dream of some day settling humans on Mars see).

In short, the search for evidence of the past and later evolution of Mars continues. This search is ongoing and is picking up speed, giving scientists the opportunity to test long-held hypotheses and revise previous ideas. Every clue is another piece of the puzzle!

Further reading: PSI

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