Sometimes, you can only find out what something is by clarifying what it is not. Astronomers are studying dark matter in a similar conceit — observing how the elusive substance behaves during collisions between vast collections of galaxies known as galaxy clusters, within which dark matter permeates and interactions between the substance occur naturally.

A team of astronomers, led by David Harvey Harvey of the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, used data from the NASA/ESA Hubble Space Telescope and NASA’s Chandra X-ray Observatory to study 72 cosmic collisions. The results were published in the journal Science on March 27, 2015.

During these cosmic collisions, clouds of gas blanketing galaxy clusters crash violently and cause each other to slow down and stop. By studying these cosmic events from different angles, the team was able to find that the dark matter pummeled through each other without stopping, showing that the elusive substance interacts less with itself than previously thought.

This narrows down the range of possible candidates for the mysterious material, limiting unknowns for particle physicists as they continue to construct or refine existing models.

This week, NASA released Hubble observations in a newscast that suggests Jupiter’s largest moon, Ganymede, possesses a subterranean saltwater ocean, enlisting its membership in a growing list of water-containing solar system locales, which include Europa, a sibling moon orbiting Jupiter, and Saturn’s moon Enceladus.

The ocean was detected by virtue of Ganymede’s privileged position in the solar system as the only moon with a magnetic field, giving it a visible aurora similar to Earth’s Northern lights. Since the moon is located close to Jupiter, changes in the red giant’s magnetic field causes the aurora to shift, influencing a predicted rocking motion of six degrees.

Assuming that Ganymede’s interior consisted of an electrically conductive fluid, a team of scientist’s led by Joachim Saur, a geophysicist at the University of Cologne in Germany, predicted that the secondary magnetic field thus generated could fight against Jupiter’s pull on the aurora. This prediction was confirmed by NASA’s Hubble Space Telescope, which measured a rocking of about two degrees, consistent with the presence of an underground ocean. This adds yet another discovery to Hubble’s history, which celebrates 25 years of groundbreaking science on April 24.

According to new behavioral science research from the University of Texas at Austin, there have been evolutionary pressures in our history that have influenced modern man’s preference for women with curvy backsides.

The research, led by UT Austin alumnus and Bilkent University psychologist David Lewis, looked at a spinal feature pronounce in females known as vertebral wedging, which affects the actual curvature of women’s lower backs. The study had about 100 men rate the attractiveness of multiple manipulated images that displayed a range of natural spinal curvatures. Top-rated images featured women possessing the hypothesized “optimum” 45.5-degree of lumbar curvature.

In order to assess whether this observed angle preference in men was due to the reflection of a larger buttock size or that of the lumbar curvature itself, approximately 200 men were shown images of women differing in both the vertical wedging and size of their buttocks. Men consistently singled out images featuring the optimum spinal curvature, regardless of buttock size.

According to the lead authors, there is good reason to the preference of this angle, as it would have better supported pregnant women during tasks of foraging and giving them the capacity to carry out multiple pregnancies without injury. The research was published online last month in Evolution and Human Behavior.