All posts by Tom



We need more missions like Cassini going to other as yet unexplored planets. Have a look at our Mimas page

The original caption:

Shadows cast across Mimas’ defining feature, Herschel Crater, provide an indication of the size of the crater’s towering walls and central peak.

Named after the icy moon’s discoverer, astronomer William Herschel, the crater stretches 86 miles (139 kilometers) wide — almost one-third of the diameter of Mimas (246 miles or 396 kilometers) itself.

Large impact craters often have peaks in their center — see Tethys’ large crater Odysseus in PIA08400. Herschel’s peak stands nearly as tall as Mount Everest on Earth.

This view looks toward the anti-Saturn hemisphere of Mimas. North on Mimas is up and rotated 21 degrees to the left. The image was taken with the Cassini spacecraft narrow-angle camera on Oct. 22, 2016 using a combination of spectral filters which preferentially admits wavelengths of ultraviolet light centered at 338 nanometers.

The view was acquired at a distance of approximately 115,000 miles (185,000 kilometers) from Mimas and at a Sun-Mimas-spacecraft, or phase, angle of 20 degrees. Image scale is 3,300 feet (1 kilometer) per pixel.

Credit: NASA/JPL-Caltech/Space Science Institute

Active Galactic Nucleus


The galaxy above called IC-3639 has an Active Galactic Nucleus that is actually obscured which leads to even more questions.  AGN’s are super-massive black holes (in the order of a million to probably hundreds of million solar masses) that are accreting massive amounts of matter, which is to say “feeding”. The accretion disc makes the Active Galaxies among the brightest objects in terms of electromagnetic radiation, so bright it is not often whether or not a galaxy is active, is in question, IC 3639 is such a galaxy.

A word about black holes in general because some people have a mistaken impression of black holes as marauding monsters roaming the universe looking for innocent planets to swallow up, that just came up on an outing with friends. No, a black holes don’t really do that. In fact if you took a black hole of one-solar-mass and swapped it with our Sun our solar system would just keep right on going just like it does now, aside from light and heat of course, the fabric of space-time would be just as it is now.

From NuSTAR:
IC 3639, a galaxy with an active galactic nucleus, is seen in this image combining data from the Hubble Space Telescope and the European Southern Observatory.

This galaxy contains an example of a supermassive black hole hidden by gas and dust. Researchers analyzed NuSTAR data from this object and compared them with previous observations from NASA’s Chandra X-Ray Observatory and the Japanese-led Suzaku satellite. The findings from NuSTAR, which is more sensitive to higher energy X-rays than these observatories, confirm the nature of IC 3639 as an active galactic nucleus that is heavily obscured, and intrinsically much brighter than observed.

NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR’s mission operations center is at UC Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center. ASI provides the mission’s ground station and a mirror archive. JPL is managed by Caltech for NASA.

Image and caption: NASA/JPL-Caltech/ESO/STScI

Looking At Home

A beautiful sight and one that could be seen by humans in the not too distant future.  This image was taken from the Mars Reconnaissance Orbiter and took a bit of processing, however I suspect at some point in a voyage to Mars the travelers would see this very sight.

I wonder if looking back at this from a craft heading to Mars, if second thoughts come to mind.


About the image from NASA

This composite image of Earth and its moon, as seen from Mars, combines the best Earth image with the best moon image from four sets of images acquired on Nov. 20, 2016, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter.

Each was separately processed prior to combining them so that the moon is bright enough to see. The moon is much darker than Earth and would barely be visible at the same brightness scale as Earth. The combined view retains the correct sizes and positions of the two bodies relative to each other.

HiRISE takes images in three wavelength bands: infrared, red, and blue-green. These are displayed here as red, green, and blue, respectively. This is similar to Landsat images in which vegetation appears red. The reddish feature in the middle of the Earth image is Australia. Southeast Asia appears as the reddish area (due to vegetation) near the top; Antarctica is the bright blob at bottom-left. Other bright areas are clouds.

These images were acquired for calibration of HiRISE data, since the spectral reflectance of the Moon’s near side is very well known. When the component images were taken, Mars was about 127 million miles (205 million kilometers) from Earth. A previous HiRISE image of Earth and the moon is online at PIA10244.

Credit: NASA/JPL-Caltech/Univ. of Arizona

Edit: the could – well debacle was fixed, tried to get “fancy” – fail lol.

The Light Study

The Power of Light shows us how NASA is dealing with something pretty common in space but we hardly give a thought, in terms of what life in space must be like.



Psyche: Journey to a Metal World from School of Earth & Space on Vimeo.

Psyche is a mission proposed by Arizona State University. It is named after 16 Psyche a very interesting minor planet in the asteroid belt.

Arizona State University (School of Earth and Space Exploration) has a very nice web-page outlining the mission and the asteroid – well worth the visit.

The big news is that Psyche HAS been selected as one of the two Discovery missions. The probable launch date is in 2023. Congratulations to ASU!

The other mission is called appropriately named Lucy and it involves what are called fossils of planetary formation, namely Trojan asteroids in Jupiter’s orbit.

Lucy Mission (pdf file).

The NASA announcement about the two missions with very good descriptions of both.

We’re At Perihelion!

Many people believe that the December solstice marks the point were the Earth’s orbit takes it closest to the sun.  It turns out the tilt of the Earth (and what determines day length) and where it is in orbit do not quite coincide.


Today at 14:18 UTC the Earth reaches perihelion, the closest we get to the Sun in our orbit.

So happy perihelion everybody!!


Sunny Saturn


The sunny northern hemisphere on Saturn.

Sunlight truly has come to Saturn’s north pole. The whole northern region is bathed in sunlight in this view from late 2016, feeble though the light may be at Saturn’s distant domain in the solar system.

The hexagon-shaped jet-stream is fully illuminated here. In this image, the planet appears darker in regions where the cloud deck is lower, such the region interior to the hexagon. Mission experts on Saturn’s atmosphere are taking advantage of the season and Cassini’s favorable viewing geometry to study this and other weather patterns as Saturn’s northern hemisphere approaches Summer solstice.

This view looks toward the sunlit side of the rings from about 51 degrees above the ring plane. The image was taken with the Cassini spacecraft wide-angle camera on Sept. 9, 2016 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 728 nanometers.

The view was obtained at a distance of approximately 750,000 miles (1.2 million kilometers) from Saturn. Image scale is 46 miles (74 kilometers) per pixel.

Credit: NASA/JPL-Caltech/Space Science Institute

The 2016 Time Adjustment

I wonder if when the new year rang in if the countdown included the extra second that was added to the world clocks. Probably not and while it might not seem like much,  the time change is important to our view of the world thanks to our modern technology even if we don’t realize it.

We have added 27  “leap-seconds” to the clock since the practice started in 1972. Read more about adding leap-seconds.


From (mostly) NASA:   On Dec. 31, 2016, official clocks around the world added a leap second just before midnight Coordinated Universal Time — which corresponds to 6:59:59 p.m. EST. NASA missions also had to make the switch, including the Solar Dynamics Observatory, or SDO, which watches the sun 24/7.

Clocks do this to keep in sync with Earth’s rotation, which gradually slows down over time. When the dinosaurs roamed Earth, for example, our globe took only 23 hours to make a complete rotation. In space, millisecond accuracy is crucial to understanding how satellites orbit.

“SDO moves about 1.9 miles every second,” said Dean Pesnell, the project scientist for SDO at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “So does every other object in orbit near SDO. We all have to use the same time to make sure our collision avoidance programs are accurate. So we all add a leap second to the end of 2016, delaying 2017 by one second.”

The leap second is also key to making sure that SDO is in sync with the Coordinated Universal Time, or UTC, used to label each of its images. SDO has a clock that counts the number of seconds since the beginning of the mission. To convert that count to UTC requires knowing just how many leap seconds have been added to Earth-bound clocks since the mission started. When the spacecraft wants to provide a time in UTC, it calls a software module that takes into consideration both the mission’s second count and the number of leap seconds — and then returns a time in UTC.

Credit: NASA/SDO