Daniel Apai, University of Arizona The search for life beyond Earth is a key driver of modern astronomy and planetary science. The U.S. is building multiple major telescopes and planetary probes to advance this search. However, the signs of life – called biosignatures – that scientists may find will likely be difficult to interpret. Figuring out where exactly to look also remains challenging. I am an astrophysicist and astrobiologist with over 20 years of experience studying extrasolar planets – which are planets beyond our solar system. My colleagues and I have developed a new approach that will identify the most interesting planets or moons to search for life and help interpret potential biosignatures. We do this by modeling how different organisms may fare in different environments, informed by studies of limits of life on Earth.

New telescopes to search for life

Astronomers are developing plans and technology for increasingly powerful space telescopes. For instance, NASA is working on its proposed Habitable Worlds Observatory, which would take ultrasharp images that directly show the planets orbiting nearby stars. My colleagues and I are developing another concept, the Nautilus space telescope constellation, which is designed to study hundreds of potentially Earthlike planets as they pass in front of their host stars.

These and other future telescopes aim to provide more sensitive studies of more alien worlds. Their development prompts two important questions: “Where to look?” and “Are the environments where we think we see signs of life actually habitable?” The strongly disputed claims of potential signs of life in the exoplanet K2-18b, announced in April 2025, and previous similar claims in Venus, show how difficult it is to conclusively identify the presence of life from remote-sensing data.

When is an alien world habitable?

Oxford Languages defines “habitable” as “suitable or good enough to live in.” But how do scientists know what is “good enough to live in” for extraterrestrial organisms? Could alien microbes frolic in lakes of boiling acid or frigid liquid methane, or float in water droplets in Venus’ upper atmosphere? To keep it simple, NASA’s mantra has been “follow the water.” This makes sense – water is essential for all Earth life we know of. A planet with liquid water would also have a temperate environment. It wouldn’t be so cold that it slows down chemical reactions, nor would it be so hot that it destroys the complex molecules necessary for life. However, with astronomers’ rapidly growing capabilities for characterizing alien worlds, astrobiologists need an approach that is more quantitative and nuanced than the water or no-water classification.

A community effort

As part of the NASA-funded Alien Earths project that I lead, astrobiologist Rory Barnes and I worked on this problem with a group of experts – astrobiologists, planetary scientists, exoplanet experts, ecologists, biologists and chemists – drawn from the largest network of exoplanet and astrobiology researchers, NASA’s Nexus for Exoplanet System Science, or NExSS. Over a hundred colleagues provided us with ideas, and two questions came up often: First, how do we know what life needs, if we do not understand the full range of extraterrestrial life? Scientists know a lot about life on Earth, but most astrobiologists agree that more exotic types of life – perhaps based on different combinations of chemical elements and solvents – are possible. How do we determine what conditions those other types of life may require? Second, the approach has to work with incomplete data. Potential sites for life beyond Earth – “extrasolar habitats” – are very difficult to study directly, and often impossible to visit and sample. For example, the Martian subsurface remains mostly out of our reach. Places like Jupiter’s moon Europa’s and Saturn’s Moon Enceladus’ subsurface oceans and all extrasolar planets remain practically unreachable. Scientists study them indirectly, often only using remote observations. These measurements can’t tell you as much as actual samples would.

To make matters worse, measurements often have uncertainties. For example, we may be only 88% confident that water vapor is present in an exoplanet’s atmosphere. Our framework has to be able to work with small amounts of data and handle uncertainties. And, we need to accept that the answers will often not be black or white.

A new approach to habitability

The new approach, called the quantitative habitability framework, has two distinguishing features: First, we moved away from trying to answer the vague “habitable to life” question and narrowed it to a more specific and practically answerable question: Would the conditions in the habitat – as we know them – allow a specific (known or yet unknown) species or ecosystem to survive? Even on Earth, organisms require different conditions to survive – there are no camels in Antarctica. By talking about specific organisms, we made the question easier to answer. Second, the quantitative habitability framework does not insist on black-or-white answers. It compares computer models to calculate a probabilistic answer. Instead of assuming that liquid water is a key limiting factor, we compare our understanding of the conditions an organism requires (the “organism model”) with our understanding of the conditions present in the environment (the “habitat model”). Both have uncertainties. Our understanding of each can be incomplete. Yet, we can handle the uncertainties mathematically. By comparing the two models, we can determine the probability that an organism and a habitat are compatible. As a simplistic example, our habitat model for Antarctica may state that temperatures are often below freezing. And our organism model for a camel may state that it does not survive long in cold temperatures. Unsurprisingly, we would correctly predict a near-zero probability that Antarctica is a good habitat for camels.

We had a blast working on this project. To study the limits of life, we collected literature data on extreme organisms, from insects that live in the Himalayas at high altitudes and low temperatures to microorganisms that flourish in hydrothermal vents on the ocean floor and feed on chemical energy. We explored, via our models, whether they may survive in the Martian subsurface or in Europa’s oceans. We also investigated if marine bacteria that produce oxygen in Earth’s oceans could potentially survive on known extrasolar planets. Although comprehensive and detailed, this approach makes important simplifications. For example, it does not yet model how life may shape the planet, nor does it account for the full array of nutrients organisms may need. These simplifications are by design. In most of the environments we currently study, we know too little about the conditions to meaningfully attempt such models – except for some solar system bodies, such as Saturn’s Enceladus. The quantitative habitability framework allows my team to answer questions like whether astrobiologists might be interested in a subsurface location on Mars, given the available data, or whether astronomers should turn their telescopes to planet A or planet B while searching for life. Our framework is available as an open-source computer model, which astrobiologists can now readily use and further develop to help with current and future projects. If scientists do detect a potential signature of life, this approach can help assess if the environment where it is detected can actually support the type of life that leads to the signature detected. Our next steps will be to build a database of terrestrial organisms that live in extreme environments and represent the limits of life. To this data, we can also add models for hypothetical alien life. By integrating those into the quantitative habitability framework, we will be able to work out scenarios, interpret new data coming from other worlds and guide the search for signatures of life beyond Earth – in our solar system and beyond. Daniel Apai, Associate Dean for Research and Professor of Astronomy and Planetary Sciences, University of Arizona This article is republished from The Conversation under a Creative Commons license. Read the original article.

Jonathan P. Stewart, University of California, Los Angeles and Lucy Arendt, St. Norbert College Earthquakes and the damage they cause are apolitical. Collectively, we either prepare for future earthquakes or the population eventually pays the price. The earthquakes that struck Myanmar on March 28, 2025, collapsing buildings and causing more than 3,000 deaths, were a sobering reminder of the risks and the need for preparation. In the U.S., this preparation hinges in large part on the expertise of scientists and engineers in federal agencies who develop earthquake hazard models and contribute to the creation of building codes designed to ensure homes, high-rises and other structures won’t collapse when the ground shakes. Local communities and states decide whether to adopt building code documents. But those documents and other essential resources are developed through programs supported by federal agencies working in partnership with practicing engineers and earthquake experts at universities. This essential federal role is illustrated by two programs that we work closely with as an earthquake engineer and a disaster management expert whose work focuses on seismic risk.

Improving building codes

First, seismologists and earthquake engineers at the U.S. Geological Survey, or USGS, produce the National Seismic Hazard Model. These maps, based on research into earthquake sources such as faults and how seismic waves move through the earth’s crust, are used to determine the forces that structures in each community should be designed to resist. A steering committee of earthquake experts from the private sector and universities works with USGS to ensure that the National Seismic Hazard Model implements the best available science.

Second, the Federal Emergency Management Agency, FEMA, supports the process for periodically updating building codes. That includes supporting the work of the National Institute of Building Sciences’ Provisions Update Committee, which recommends building code revisions based on investigations of earthquake damage. More broadly, FEMA, the USGS, the National Institute of Standards and Technology and the National Science Foundation work together through the National Earthquake Hazards Reduction Program to advance earthquake science and turn knowledge of earthquake risks into safer standards, better building design and education. Some of those agencies have been threatened by potential job and funding cuts under the Trump administration, and others face uncertainty regarding continuation of federal support for their work. It is in large part because of the National Seismic Hazard Model and regularly updated building codes that U.S. buildings designed to meet modern code requirements are considered among the safest in the world, despite substantial seismic hazards in several states. This paradigm has been made possible by the technical expertise and lack of political agendas among the federal staff. Without that professionalism, we believe experts from outside the federal government would be less likely to donate their time. The impacts of these and other programs are well documented. We can point to the limited fatalities from U.S. earthquakes such as the 1989 Loma Prieta earthquake near San Francisco, the 1994 Northridge earthquake in Los Angeles and the 2001 Nisqually earthquake near Seattle. Powerful earthquakes in countries lacking seismic preparedness, often due to lack of adoption or enforcement of building codes, have produced much greater devastation and loss of life.

The US has long relied on people with expertise

These programs and the federal agencies supporting them have benefited from a high level of staff expertise because hiring and advancement processes have been divorced from politics and focused on qualifications and merit. This has not always been the case. For much of early U.S. history, federal jobs were awarded through a patronage system, where political loyalty determined employment. As described in “The Federal Civil Service System and The Problem of Bureaucracy,” this system led to widespread corruption and dysfunction, with officials focused more on managing quid pro quo patronage than governing effectively. That peaked in 1881 with President James Garfield’s assassination by Charles Guiteau, a disgruntled supporter who had been denied a government appointment. The passage of the Pendleton Act by Congress in 1883 shifted federal employment to a merit-based system. This preference for a merit-based system was reinforced in the Civil Service Reform Act of 1978. It states as national policy that “to provide the people of the United States with a competent, honest, and productive workforce … and to improve the quality of public service, Federal personnel management should be implemented consistent with merit system principles.” The shift away from a patronage system produced a more stable and efficient federal workforce, which has enabled improvements in many critical areas, including seismic safety and disaster response.

Merit-based civil service matters for safety

While the work of these federal employees often goes unnoticed, the benefits are demonstrable and widespread. That becomes most apparent when disasters strike and buildings that meet modern code requirements remain standing. A merit-based civil service is not just a democratic ideal but a proven necessity for the safety and security of the American people, one we hope will continue well into the future. This can be achieved by retaining federal scientists and engineers and supporting the essential work of federal agencies. This article, originally published March 31, 2025, has been updated with the rising death toll in Myanamar. Jonathan P. Stewart, Professor of Engineering, University of California, Los Angeles and Lucy Arendt, Professor of Business Administration Management, St. Norbert College This article is republished from The Conversation under a Creative Commons license. Read the original article.