All posts by C.C. Petersen

Flipping through Curiosity’s Album

A sea of dunes, as seen by Curiosity Rover's right NAVCAM, taken on Sol 753. Courtesy NASA/JPL

A sea of dunes, as seen by Curiosity Rover’s right NAVCAM, taken on Sol 753. Courtesy NASA/JPL Click for an enlarged view.

Every once in a while I go wandering through the raw images from the Mars Curiosity Rover. And, every time I find jaw-droppingly beautiful views. Like this one.

Wow!!!  It’s a sea of dunes stretching out toward a rock outcrop in the distance, and even farther away, a distant set of hills.

The wind blows a lot at Mars. Wind-driven erosion is an aeolian process (aeolian coming from the Greek God Aeolis, keeper of the winds). It sculpts the surface, just as winds affect and create landforms on Earth. These dunes could just as easily BE on Earth, they look that familiar!

The scene poses a lot of questions:  what are the factors that lend themselves to forming these lovely dunes?  What are those rocks in the foreground? Have the dunes “walked over” them as the winds blew? What’s the white flat area right head of the rover?

I wonder if the rover will try to drive across this sea of dunes? Could be risky.  Is there another route to be taken?

After I stared for a while at this lovely sea of interlocking dunes, I found another image taken the same day that shows a view in a slightly different direction.

Curiosity's raw view of a scene on Mars. Courtesy NASA/JPL

Curiosity’s raw view of a scene on Mars. Courtesy NASA/JPL

The pebbly surface is interrupted by rock outcrops, more small dunes, and at the bottom, what must be edge of the dune field from the other image. To someone who lives in a fairly arid environment (as I do) or who has visited the desert Southwest of the U.S. (as I have), this looks so achingly familiar. It’s like I could just hop out of the Jeep and go striding across the surface to pick up some rocks. Except, this geology field trip is tens of millions of kilometers away, on a planet that looks a lot like Earth.

Images like these two (and many others taken by the rovers and landers on Mars) are a triumph of planetary exploration. They give us a “first hand” sense of what it’s like to be there. Of course, Mars’s atmosphere is thin and made of carbon dioxide, so if I WERE there, I’d be wearing a space suit, carrying oxygen, and shading myself from the higher ultraviolet radiation exposure.

You know, that’s exactly what future Mars explorers will face: these dry and dusty desert landscapes, bright sunlight, UV radiation, windy weather, and cold temperatures. The rovers, in sending back images like these, are really preparing us mentally for what our explorers will find. It won’t be just those folks who make the trip who go to Mars. The rest of us will go along too, in spirit, in imagination, in awe and wonder. And, as I flip through Curiosity’s picture album tonight, I’m along for the ride. You can do it, too.  Mars is a mouse click away!

Monster Galaxies Nibble On Smaller Ones to Get  Bigger

Some of the many thousands of merging galaxies as seen by the Galaxy and Mass Assembly (GAMA) Survey. Courtesy Professor Simon Driver and Dr Aaron Robotham, ICRAR

Galaxies grow by eating other galaxies — that’s a given in the cosmos. It’s also true that galaxies spend much of their productive lives making stars from the gas they contain. These two galactic activities began with the first proto-galactic “shreds” that began to combine to grow today’s galaxies. It has continued ever since.

The Milky Way is a good example of this. It formed some 13 billion years ago and grew larger by consuming stars and gas from other, smaller galaxies. It is, in fact, still cannibalizing some dwarf galaxies and may eventually gobble up the Large and Small Magellanic Clouds in a few billion years.

In the future, the Milky Way and the Andromeda Galaxy — currently some 2.5 million light-years apart — will collide. It’s very likely that the  much-more-massive Andromeda will cannibalize the Milky Way. Ultimately the new galaxy that’s formed will undergo a superburst of star formation, using up the gases from the two combined galaxies. Astronomers have seen massive starburst knots at other galaxy collisions, so it’s very likely a feature of most galaxy collisions.

Researchers are now working to pin down some of the complexities of this galaxy-evolution-by-cannibalism mechanism. A team  in Australia is using spectroscopic observations 0f light and radio waves from distant galaxies to find many sites where galaxies are merging, larger ones pigging out on smaller ones. Interestingly, although the galaxies undergo starburst events during the mergers, eventually many of the most massive galaxies created from these collisions eventually stop making stars. The reasons may be related to events occurring within their active central cores (where many galaxies have supermassive black holes that could be sending jets out to space and somehow disrupting the normal course of events).

The group studied many merging galaxies and characterized the shapes they saw. Each of the galaxies in the image at the left from their survey captures a galaxy collision in a snapshot of time. You can see some are about to merge and others have passed by each other, interacted, and are about to go for a second pass. Ultimately each of these mergers will result in a monster galaxy.

The group also created an animation from a computer model showing the interaction of the Milky Way and Andromeda, which will commence in about five billion years. Ultimately, both galaxies will lose their separate identities and become a new, more massive version of the originals.

Andromeda and the Milky Way Collide! from ICRAR on VimeoIn about five billion years time, nearby massive galaxy Andromeda will merge with our own galaxy, the Milky Way, in an act of galactic cannibalism (technically Andromeda will be eating us, as it’s the bigger of the two galaxies.). There haven’t been any large mergers with our galaxy recently, but we can see the remnants of galaxies that have previously been snacked on by the Milky Way. We’re also going to eat two nearby dwarf galaxies, the Large and Small Magellanic Clouds sometime in the future.
This simulation shows what will happen when the Milky Way and Andromeda get closer together and then collide, and then finally come together once more to merge into an even bigger galaxy.
Simulation Credit: Prof Chris power (ICRAR-UWA), Dr Alex Hobbs (ETH Zurich), Prof Justin Reid (University of Surrey), Dr Dave Cole (University of Central Lancashire) and the Theoretical Astrophysics Group at the University of Leicester.Video Production Credit: Pete Wheeler, ICRAR.

In the far distant figure, many billions of years from now, galaxies in clusters and groups will likely have merged into a few supergiant monster galaxies. This will markedly change the look of the cosmos in ways that astronomers can now only speculate about. Stay tuned!