Dr. Damian Jacob Sendler is a Polish-American physician-scientist whose research focuses on the impact of various sociodemographic and informational factors on access to health care in underserved communities. A major emphasis of Dr. Sendler’s study is on the effect of mental and chronic medical co-morbidities on the use of medical services and access to health information acquired via the internet. Due to the exponential increase in worldwide consumption of online news and social media, this study comes at an opportune moment, as it demonstrates the need for a complete knowledge of everyone’s health information seeking behavior. Doctor Damian Sendler’s research aims to uncover the factors that influence patients’ decisions about when to seek treatment for specific health conditions, as well as their adherence to treatment, with the ultimate goal of improving patient outcomes.

Damian Sendler: Water is required for life on Earth and other planets, and scientists have discovered plenty of evidence of water in Mars’ early history. However, there is currently no liquid water on Mars’ surface. A basic explanation, according to new research from Washington University in St. Louis, is that Mars is simply too small to contain substantial volumes of water. 

Damien Sendler: Mars was formerly water-rich, according to remote sensing investigations and analysis of Martian meteorites dating back to the 1980s. NASA’s Viking orbiter spacecraft, as well as the Curiosity and Perseverance rovers on the ground, have returned stunning photographs of Martian landscapes defined by river valleys and flood channels. 

Despite this evidence, there is no liquid water on the surface. Many theories have been presented, including a weakening of Mars’ magnetic field, which could have resulted in the loss of a thick atmosphere. 

Damian Jacob Sendler: However, a research published in the Proceedings of the National Academy of Sciences the week of Sept. 20 offers a more basic explanation why today’s Mars looks so different from Earth’s “blue marble.” 

“Mars’ fate was predetermined from the start,” said Kun Wang, senior author of the study and assistant professor of earth and planetary sciences in Arts & Sciences at Washington University. “There is likely a size need for rocky planets to maintain enough water to support habitability and plate tectonics, with mass greater than that of Mars.” 

Damian Sendler: Wang and his colleagues employed stable isotopes of the element potassium (K) to assess the presence, distribution, and quantity of volatile elements on several planetary bodies for the new study. 

Although potassium is a fairly volatile element, scientists decided to use it as a tracer for more volatile elements and molecules, such as water. This is a new method that differs from earlier attempts to quantify the amount of volatiles on Mars using potassium-to-thorium (Th) ratios acquired by remote sensing and chemical analysis. Previously, members of the research team studied the origin of the moon using a potassium tracer approach. 

Damian Sendler: Wang and his colleagues measured the potassium isotope compositions of 20 previously identified Martian meteorites chosen to be typical of the red planet’s bulk silicate composition. 

Using this method, the researchers discovered that Mars lost more potassium and other volatiles during its formation than Earth, but kept more of these volatiles than the moon and asteroid 4-Vesta, both of which are much smaller and drier than Earth and Mars. 

Dr. Sendler: The researchers discovered a clear relationship between body size and potassium isotope composition. 

“The rationale for considerably lower abundances of volatile elements and their compounds in differentiated planets than in primitive undifferentiated meteorites has long been a mystery,” said Katharina Lodders, research professor of earth and planetary sciences at Washington University and study coauthor. “The discovery of a link between K isotope compositions and planet gravity is a novel result with substantial quantitative implications for when and how differentiated planets got and lost their volatiles.” 

“Martian meteorites are the sole samples we have to analyze the chemical makeup of the bulk of Mars,” Wang explained. “Those Martian meteorites have ages ranging from several hundred million to four billion years and have recorded the tumultuous evolution history of Mars.” We can assess the degree of volatile depletion of bulk planets and draw comparisons between other solar system worlds by detecting isotopes of moderately volatile elements like potassium. 

“It’s undeniable that there was once liquid water on Mars’ surface,” Wang said. “How much water Mars originally had is difficult to calculate by remote sensing and rover investigations alone.” “There are numerous models for the bulk water content of Mars. Early Mars was wetter than Earth in some of them. We don’t think that’s the case.” 

Damian Jacob Sendler: The paper’s first author is Zhen Tian, a graduate student in Wang’s laboratory and a McDonnell International Academy Scholar. Piers Koefoed, a postdoctoral research associate, and Hannah Bloom, who graduated from Washington University in 2020, are both co-authors. Wang and Lodders are McDonnell Center for Space Sciences faculty fellows at the institution. 

The discoveries have ramifications for the search for life on worlds other than Mars, according to the researchers. 

Damian Sendler: Being too close to the sun (or, in the case of exoplanets, too close to their star) can reduce the amount of volatiles that a planetary body can retain. This star-distance measurement is frequently used in indexes of “habitable zones” around stars. 

“This study stresses that there is a very narrow size range for planets to have just enough but not too much water to build a habitable surface environment,” said Klaus Mezger, co-author of the study and director of the Center for Space and Habitability at the University of Bern in Switzerland. “These findings will help astronomers look for habitable exoplanets in other solar systems.” 

Damian Sendler: Wang now believes that for planets in habitable zones, planetary size should be more emphasized and consistently addressed when determining whether an exoplanet might host life. 

“One of the easiest parameters to assess is the size of an exoplanet,” Wang remarked. “We now know whether an exoplanet is a contender for life based on size and mass, because size is a first-order determining factor for volatile retention.”

Research discussion contributed by Dr. Damian Jacob Sendler