Ula-Ula man's island

A View of Mercury From Afar

This image of Mercury, acquired by the Mercury Dual Imaging System (MDIS) aboard NASA’s MESSENGER mission on April 23, 2013, allows us to take a step back to view the planet. Prior to the MESSENGER mission, Mercury’s surface was often compared to the surface of Earth’s moon, when in fact, Mercury and the moon are very different. This image in particular highlights many basins near Mercury’s terminator, including Bach crater. Many craters with central peaks and the nearby bright rays of Han Kan crater are also evident.
Once per week, MDIS captures images of Mercury’s limb, with an emphasis on imaging the southern hemisphere limb. These limb images provide information about Mercury’s shape and complement measurements of topography made by the Mercury Laser Altimeter (MLA) of Mercury’s northern hemisphere.

Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Hemoglobin: Binding O₂: Cooperation Makes It Easier

The gorgeous and colourful animination above, from the Research Collaboratory for Structural Bioinformatics Protein Data Bank (RCSB PDB), illustrates the conformational change upon oxygen binding to hemoglobin⁽¹⁾.

What is hemoglobin?
Hemoglobin is a remarkable metalloprotein (a protein that contains a metal ion), found in red blood cells, that plays an important role in oxygen transport. Hemoglobin is a heterotetramer consisting of 2 α subunits (light pink and the other one can’t be seen) and 2 β subunits (light purple and light blue), arranged in 2 αβ subunits (2 sets of dimers). Each subunit contains one heme group (red) — a protoporphyrin ring with Fe²⁺ in the ring centre — resulting in four heme groups in total.⁽²⁾

How does hemoglobin bind O₂?
Interestingly, hemoglobin binds O₂ (teal) cooperatively: when one heme group binds to O₂, it increases the other heme groups’ affinity (ability to bind) for O₂. This is a type of allosteric interaction — the change in shape of a protein that results from binding of a molecule at the allosteric site (a site other than the active site).⁽²⁾

Why does this happen?
When O₂ is not bound (deoxy), Fe²⁺ lies a little outside of the protoporphyrin ring. When O₂ is bound (oxy), Fe²⁺ ”pops” into the ring, pulling with it a histidine (yellow), His, residue. Also attached to His is an α-helix (orange), which also shifts. All of this movement disrupts and forms new interactions between the α₁β₁-α₂β₂ interface.⁽¹⁾ It is this conformational change that increases the other hemes’ ability to bind to O₂. Noticeably, as more O₂ binds to hemoglobin, the α₁β₁ dimer will rotate 15° relative to the α₂β₂ dimer, which can be observed in the animation.²

(1) Goodsell, D., & Dutta, S. (2003). Hemoglobin RCSB Protein Data Bank DOI: 10.2210/rcsb_pdb/mom_2003_5
(2) Krisinger, M. BIOC 202 Lecture on Protein Function. Presented at the University of British Columbia. May 27, 2013.

original post by atomicallena via scientificillustration

The Moon and the Sun

Two or three times a year, NASA’s Solar Dynamics Observatory observes the moon traveling across the sun, blocking its view. While this obscures solar observations for a short while, it offers the chance for an interesting view of the shadow of the moon. The moon’s crisp horizon can be seen up against the sun, because the moon does not have an atmosphere. (At other times of the year, when Earth blocks SDO’s view, the Earth’s horizon looks fuzzy due to its atmosphere.)
If one looks closely at such a crisp border, the features of the moon’s topography are visible, as is the case in this image from Oct. 7, 2010. This recently inspired two NASA visualizers to overlay a 3-dimensional model of the moon based on data from NASA’s Lunar Reconnaissance Orbiter, or LRO, into the shadow of the SDO image. Such a task is fairly tricky, as the visualizers — Scott Wiessinger who typically works with the SDO imagery and Ernie Wright who works with the LRO imagery — had to precisely match up data from the correct time and viewpoint for the two separate instruments. The end result is an awe-inspiring image of the sun and the moon.

Image Credit: NASA/SDO/LRO/GSFC

In the Vortex of Power

John Wargo, lead technician at NASA Glenn’s Propulsion System Laboratory (PSL) is performing an inspection on the inlet ducting, upstream of the Honeywell ALF 502 engine that was recently used for the NASA Engine Icing Validation test.
This test allows engine manufacturers to simulate flying through the upper atmosphere where large amounts of icing particles can be ingested and cause flame outs or a loss of engine power on aircraft. This test was the first of its kind in the world and was highly successful in validating PSL’s new capability. No other engine test facility has this capability.
Glenn is working with industry to address this aviation issue by establishing a capability that will allow engines to be operated at the same temperature and pressure conditions experienced in flight, with ice particles being ingested into full scale engines to simulate flight through a deep convective cloud.
The information gained through performing these tests will also be used to establish test methods and techniques for the study of engine icing in new and existing commercial engines, and to develop data required for advanced computer codes that can be specifically applied to assess an engine’s susceptibility to icing in terms of its safety, performance and operability.

Image Credit: NASA
Bridget R. Caswell (Wyle Information Systems, LLC)

Cheshire Moon by Chepar

via scinerds, kenobi-wan-obi

The Butterfly Nebula

The bright clusters and nebulae of planet Earth’s night sky are often named for flowers or insects. Though its wingspan covers over 3 light-years, NGC 6302 is no exception. With an estimated surface temperature of about 250,000 degrees C, the dying central star of this particular planetary nebula has become exceptionally hot, shining brightly in ultraviolet light but hidden from direct view by a dense torus of dust.
This sharp and colorful close-up of the dying star’s nebula was recorded in 2009 by the Hubble Space Telescope’s Wide Field Camera 3, installed during the final shuttle servicing mission. Cutting across a bright cavity of ionized gas, the dust torus surrounding the central star is near the center of this view, almost edge-on to the line-of-sight. Molecular hydrogen has been detected in the hot star’s dusty cosmic shroud. NGC 6302 lies about 4,000 light-years away in the arachnologically correct constellation of the Scorpion (Scorpius).

Image Credit: NASA/ESA/Hubble

Valentina Tereshkova, the first woman in space via @nereide

the first woman to have flown in space, having been selected from more than four hundred applicants and five finalists to pilot Vostok 6 on 16 June 1963. In order to join the Cosmonaut Corps, Tereshkova was only honorarily inducted into the Soviet Air Force and thus she also became the first civilian to fly in space.[1] During her three-day mission, she performed various tests on herself to collect data on the female body’s reaction to spaceflight. Before being recruited as a cosmonaut, Tereshkova was a textile factory assembly worker and an amateur parachutist. After the dissolution of the first group of female cosmonauts in 1969, she became a prominent member of the Communist Party of the Soviet Union, holding various political offices. She remained politically active following the collapse of the Soviet Union and is still revered as a heroine in post-Soviet Russia.

In the image: Valentina Tereshkova and NASA astronaut Catherine Coleman at the Gagarin Cosmonaut Training Center in December 2010.

Sun Over Earth’s Horizon

The sun is captured in a “starburst” mode over Earth’s horizon by one of the Expedition 36 crew members aboard the International Space Station, as the orbital outpost was above a point in southwestern Minnesota on May 21, 2013.

Image Credit: NASA

Cosmic Collision Between Galaxies

This image from the NASA/ESA Hubble Space Telescope captures an ongoing cosmic collision between two galaxies — a spiral galaxy is in the process of colliding with a lenticular galaxy.
The image also reveals further evidence of the collision. There is a bright stream of stars coming out from the merging galaxies, extending out towards the top of the image. The bright spot in the middle of the plume, known as ESO 576-69, is what makes this image unique. This spot is believed to be the nucleus of the former spiral galaxy, which was ejected from the system during the collision and is now being shredded by tidal forces to produce the visible stellar stream.

Image Credit: European Space Agency/NASA Hubble