During the year, the Sun appears to move along a path in the sky known as the ecliptic. The Earth’s equator, or its sky equivalent called the celestial equator, is offset from the ecliptic by 23.5°. This means that for 6 months, either the northern or southern hemisphere faces towards the Sun while the other hemisphere faces away from it, then they switch for 6 months. The equinoxes mark the times when Earth’s orientation switches.

One way we know the Earth is round is that objects of the same height at different distances north or south of the equator will cast shadows of different lengths at noon on the equinox. And the angles of each shadow will be exactly equal to the latitude of the objects casting them!

Maria Calderon-Marrero is a senior at Cornell University majoring in Biology with a concentration in Microbiology and minoring in Earth and Atmospheric Sciences. As a Ronald E. McNair Scholar, she is preparing for a Ph.D. in microbial astrobiology, with a focus on how life might survive, and leave traces, on planets like Mars or ocean worlds such as Europa.

She conducts research in the Muñoz-Saez Group at Cornell University, studying microbes in the silica-rich hot springs of El Tatio, Chile, an environment that closely resembles ancient Mars. Her work investigates how biosignatures are preserved in extreme conditions to help guide future space missions. She has also contributed to research on Antarctic extremophiles and lipid biomarkers in Mars analog environments.

Maria is passionate about making science engaging and inclusive. She hopes to use astrobiology to spark curiosity and inspire students from all backgrounds, especially those historically underrepresented in STEM. Outside the lab, she enjoys nature, crafting, and exploring sci-fi and fantasy worlds through books, video games, and shows.

Maria is joining us from the Blue Marble Space Institute of Science‘s Young Scientist Program. She is developing a project with Sciworthy to communicate astrobiology through videos.

How do microbes prepare for winter? As the Earth continues its journey around the Sun, the animals and plants of the northern hemisphere are preparing for the coming winter. Humans rely on calendars to keep track of the seasons, while other organisms use changes in the weather and the amount of daylight to signal when winter is approaching. But how do microbes prepare for winter? Researchers discovered that when some bacteria sense shorter days, they boost their cell walls with extra fats to survive the freezing temperatures. Read about it here.

Seasonal frost forms on Mars. Water is essential for life, so when researchers want to explore another planet, they first locate its water resources. Astrobiologists are particularly interested in Mars due to its evidence of past water, which could have enabled life. Since the surface of Mars is cold and dry today, they want to know where that past water went. Scientists recently discovered seasonal frost accumulations on Martian volcanoes that formed from water vapor in the atmosphere. Read about it here.

Exoplanets with extreme seasons might be more habitable. Earth’s relative distance to the Sun month-to-month doesn’t influence the climate much because its orbit is close to a perfect circle, as described above. But exoplanets with non-circular orbits could experience extreme seasonal changes. Astronomers have shown that these exoplanets with weird orbits could actually be more habitable than planets with circular orbits. Somewhere in the Galaxy, alien microbes could be enjoying a scorching, irradiated summer and a subzero, icy winter. Read about it here.