A congregation of alligators in Cambodia, 2008
Digital Terrain Models (DTMs) allow scientists to ‘stand’ on planetary surfaces. Although ordinary images can give spectacular bird’s-eye views, they can only convey part of the picture. They miss out on the topography, or the vertical elevation of the surroundings. That’s where Mars Express comes in.
The DTM can instantly tell researchers the slope of hillsides or the height of cliffs, the altitude and slope of lava flows or desert plains. It also helps planetary scientists to better interpret other data sets, for example the results of the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS).
The Mars Express DTM is the most detailed topographic data set ever released for Mars. Its release has been made possible by processing individual image swaths taken by the HRSC as Mars Express sweeps through its orbit. The individual swaths are then put together into mosaics that cover large regions. The high-resolution images used have a resolution of 10 m/pixel. The DTM elevation data derived from these images is provided in pixels of up to 50 m, with a height accuracy of 10 m.
The orbit of Mars Express determines the resolution of its pictures. When it is closest to the surface, it can take the most detailed pictures.
Cephalopods of Naples
From an 1896 monograph by Giuseppe Jatta. The illustrator is Comingio Merculiano (1845- 1915), a professional watercolor painter hired in 1885 by prof. Anton Dohrn as in-house illustrator for the Naples Zoological Station, and one of the best scientific illustrators to date. This book on cephalopods is his masterpiece.
Images hosted by the Biodiversity Heritage Library on behalf of the Smithsonian Institution
there’s a species of solitary mason bees that make these pretty little nests for their larvae out of flower petals
Tanning babies at the Chicago Orphan Asylum, 1925, Chicago. The practice was used to offset rickets during the winter months.
A regular at Le Louis IX in Paris, “Caramel” keeps a client company, May 1988.
Photograph by James L. Stanfield, National Geographic