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Small-Scale Jetlike Features in Penumbral Chromospheres
Lites, B. W.; Ichimoto, K.; Tsuneta, S. +8 more
We observed fine-scale jetlike features, referred to as penumbral microjets, in chromospheres of sunspot penumbrae. The microjets were identified in image sequences of a sunspot taken through a Ca II H-line filter on the Solar Optical Telescope on board the Japanese solar physics satellite Hinode. The microjets’ small width of 400 kilometers and s…
Coupled Ferric Oxides and Sulfates on the Martian Surface
Mangold, N.; Sotin, C.; Bibring, J. -P. +9 more
The Mars Exploration Rover (MER), Opportunity, showed that layered sulfate deposits in Meridiani Planum formed during a period of rising acidic ground water. Crystalline hematite spherules formed in the deposits as a consequence of aqueous alteration and were concentrated on the surface as a lag deposit as wind eroded the softer sulfate rocks. On …
Radar Sounding of the Medusae Fossae Formation Mars: Equatorial Ice or Dry, Low-Density Deposits?
Stofan, Ellen R.; Clifford, Stephen M.; Orosei, Roberto +10 more
The equatorial Medusae Fossae Formation (MFF) is enigmatic and perhaps among the youngest geologic deposits on Mars. They are thought to be composed of volcanic ash, eolian sediments, or an ice-rich material analogous to polar layered deposits. The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) instrument aboard the Mars Expr…
Saturn’s Gravitational Field, Internal Rotation, and Interior Structure
Anderson, John D.; Schubert, Gerald
Saturn’s internal rotation period is unknown, though it must be less than 10 hours, 39 minutes, and 22 seconds, as derived from magnetic field plus kilometric radiation data. By using the Cassini spacecraft’s gravitational data, along with Pioneer and Voyager radio occultation and wind data, we obtain a rotation period of 10 hours, 32 minutes, and…
Io Volcanism Seen by New Horizons: A Major Eruption of the Tvashtar Volcano
Stern, S. A.; Weaver, H. A.; Spencer, J. R. +14 more
Jupiter’s moon Io is known to host active volcanoes. In February and March 2007, the New Horizons spacecraft obtained a global snapshot of Io’s volcanism. A 350-kilometer-high volcanic plume was seen to emanate from the Tvashtar volcano (62°N, 122°W), and its motion was observed. The plume’s morphology and dynamics support nonballistic models of l…
Saturn’s Small Inner Satellites: Clues to Their Origins
Porco, C. C.; Thomas, P. C.; Weiss, J. W. +1 more
Cassini images of Saturn’s small inner satellites (radii of less than ~100 kilometers) have yielded their sizes, shapes, and in some cases, topographies and mean densities. This information and numerical N-body simulations of accretionary growth have provided clues to their internal structures and origins. The innermost ring-region satellites have…
Slipping Magnetic Reconnection in Coronal Loops
Golub, Leon; DeLuca, Edward E.; Narukage, Noriyuki +6 more
Magnetic reconnection of solar coronal loops is the main process that causes solar flares and possibly coronal heating. In the standard model, magnetic field lines break and reconnect instantaneously at places where the field mapping is discontinuous. However, another mode may operate where the magnetic field mapping is continuous but shows steep …
Enceladus: Cosmic Graffiti Artist Caught in the Act
Verbiscer, Anne; Helfenstein, Paul; Showalter, Mark +1 more
As one of the most geologically active bodies in the solar system, Saturn's moon Enceladus not only coats itself with water ice particles, it accounts for the unusually high albedos of the other satellites orbiting within Saturn's vast, tenuous E ring. This effect is evident in Hubble Space Telescope observations obtained at true opposition on 13 …
Density of Mars’ South Polar Layered Deposits
Zuber, Maria T.; Asmar, Sami W.; Smrekar, Suzanne E. +6 more
Both poles of Mars are hidden beneath caps of layered ice. We calculated the density of the south polar layered deposits by combining the gravity field obtained from initial results of radio tracking of the Mars Reconnaissance Orbiter with existing surface topography from the Mars Orbiter Laser Altimeter on the Mars Global Surveyor spacecraft and …
Twisting Motions of Sunspot Penumbral Filaments
Kubo, M.; Lites, B. W.; Ichimoto, K. +8 more
The penumbra of a sunspot is composed of numerous thin, radially extended, bright and dark filaments carrying outward gas flows (the Evershed flow). Using high-resolution images obtained by the Solar Optical Telescope aboard the solar physics satellite Hinode, we discovered a number of penumbral bright filaments revealing twisting motions about th…