Capturing a Snapshot of Pluto’s Atmosphere. The Story of an Occultation
Published 8/19/2018 in Franck Marchis Blog Author Franck Marchis
Last Tuesday night, a large number of amateur and professional astronomers located across Mexico, the US, and Canada took advantage of a rare and exciting opportunity: observe a blinking star while Pluto occulted it. In Southern California, the SETI Institute, the Observatoire de Paris, Unistellar, and Oceanside Photo and Telescope (OPT), one of the largest telescope retailers in the world, collaborated to observe this rare event and gather the precious data we need to understand Pluto’s atmosphere and climate. Here is our story.   Like most events in the world of modern astronomy, this one started with an email. In February 2018, I sent my colleagues at the Observatoire de Paris a message letting them know that the eVscope was ready and able to observe occultations. We had by then already observed our first occultation, by main-belt asteroid 175 Andromache, from the south of France and I wanted to get input from Bruno... read more ❯

Where dunes once trod
Published 8/13/2018 in Lori Fenton's Blog Author lfenton
Mars has been dusty, and that's affecting the quality of HiRISE images (just look at the recent images in the catalog and you'll see they're not that great). That's made it hard for me to choose a good one for my blog. I suppose I could go with a grainy image and talk about things like the "cost of real data" and "one person's noise is another person's data" (because surely someone will make use of those poor-quality images to track dust clouds, or something). I'm waiting to see where the bright dust falls out on the surface, because I want to show you dust-covered dunes, and then watch how the wind slowly clears them off. It will be a bit like watching snow melt in the spring, if you live in a place that gets snow in the winter. But first I found a really neat image of missing dunes. No... read more ❯

Oh, Mars!
Published 8/2/2018 in Lori Fenton's Blog Author lfenton
The HiRISE camera has a website called HiWish that lets anybody (yes, even you!) make image requests. That's right, you can choose any spot on Mars that HiRISE can see, pick any season (or let them pick for you if you don't care), and one day the Mars Reconnaissance Orbiter's path will fly over your spot and, if it isn't scheduled for other observations, HiRISE will take your image! I've made several requests that way. Sometimes I want to get repeat coverage of an area to see if dunes and ripples have migrated - that requires both a "before" and an "after" image. Sometimes I want a closer look at something that isn't easy to figure out using other images - HiRISE is still the highest resolution camera sent to orbit Mars, so it's sort of like whipping out a magnifying glass to have a closer look at something you could... read more ❯

Spring is a messy time
Published 7/16/2018 in Lori Fenton's Blog Author lfenton
In many areas on Earth that get winter snow, spring thaw is a messy time. Frozen ground turns to mud, and there may be runoff everywhere from melting snow and spring rain. Or if you live in a place that gets winter rains, spring might be the time when mudslides are most common. Spring can be messy on Mars too, although in this case the ice isn't H2O, but CO2. Also, it's not melting, but rather sublimating. But that can still make a big mess. Here's part of a dune field in early spring, located in the high southern latitudes. Normally dunes on Mars are dark because they're made of dark sand, but here they're still mostly covered by bright wintertime frost. If you didn't already know there were dunes here, you might never guess that's what's there. Zoom in (click on the image) and you'll see the ice is draped... read more ❯

Field of barchans
Published 7/8/2018 in Lori Fenton's Blog Author lfenton
It's July, and I've had a busy summer so far. This is my first post in a few weeks - I've been out at various meetings, and last week I spent with my family on vacation. The one week of normal work I had was spent furiously working to help a colleague put together a paper. That left me no time to share pretty pictures with the world. So finally I'm back and able to make another blog post. I decided to make it simple: just a field of pretty barchans. Barchans are one of the simplest types of dunes - they're just piles of sand blown by wind coming from only one direction. The barchans here in Lyot crater are some of the smallest dunes (the smallest one here is ~60 m, or ~200 ft across, which... read more ❯

Seeing the Sombrero Galaxy Seen From Cities
Published 5/31/2018 in Franck Marchis Blog Author Franck Marchis
I am happy to share with you an update from Unistellar. Our team has recently collected a pair of images of the glorious Sombrero Galaxy (M104 in the Messier Catalog) taken during one of the most recent observing runs. Both images were taken in heavily light-polluted environments, the first near Marseille, in the south of France, on May 17 and the second from San Francisco, California on May 14. As usual, these are unedited images, and they clearly show what you can see with our eVscope prototype after just a few hundreds of seconds of observing.     Located in the constellation of Virgo, the Sombrero Galaxy is too faint to be seen with naked eye (V~8). It was discovered in 1781 by French astronomer and comet hunter Pierre Méchain, a colleague of Charles Messier, and reported independently by... read more ❯

The Mars Global Digital Dune Database
Published 5/30/2018 in Lori Fenton's Blog Author lfenton
There are a lot of dune fields on Mars. Over the last ten years I've been part of a group that's mapped out the big dark dunes on the planet to see where they form, and to understand the sedimentary and meteorological processes that control their formation. We compiled a database showing their locations and various physical characteristics. Wait, why do piles of sand form in the first place? On Earth, it's because: 1. There's a lot of sand (not a surprise). 2. There's a lot of strong wind (also not a surprise). 3. The sand is free to be moved by the wind. That is, it's not held down by vegetation, or covered by a lake, or paved over. That mostly amounts to dune fields piling up in arid places, where there's not a lot of vegetation or rainfall to stop the wind from moving sand around. And even then, you don't see piles... read more ❯

Published 5/9/2018 in Lori Fenton's Blog Author lfenton
Here's a grand dune, making its stately way northward under winds blowing mainly from the south-southeast (bottom to top), with a secondary wind blowing from the southwest (lower left to upper right). There are two rippled and sharp-crested slip faces on this dune -- can you identify both of them (hint: each wind creates one slip face on the downwind side)?   The dune is ~750 m (2,460 ft) long. It's made of dark sand the wind blows along the ground until it piles up into these big mobile hills we call dunes. But the dune isn't alone. Trailing behind the dune, like a veil, is an entourage of smaller, paler ripples. These are coarse-grained ripples, made partly of larger grains that are too heavy to move as quickly as the finer dark sand that makes up the bulk... read more ❯

Wild & dark lacy dunes on twisty bright layers
Published 4/30/2018 in Lori Fenton's Blog Author lfenton
Some windblown dunes on Mars are just beyond words. Take these beasts in this 0.95x0.95 km (0.59x0.59 mi) scene: These are a peculiar type of bedform called a transverse aeolian ridge, or TAR for short, with a spacing of about 50 m (164 ft). Nobody really understands these things: are they dunes or ripples or something totally different? They're common on Mars but unusual (maybe even nonexistent) on Earth. They're also pretty dark-toned here, whereas on most of Mars they tend to be lighter than the surrounding rocks. The TARs mostly cover the surface, but you can see bright bits poking through in places. You can see layers sweeping around - this is a place where stuff (either sediment or volcanic rock) was deposited in successive layers. It may then have been tilted or deformed, and then it was eroded away to expose the... read more ❯

Reusing old canvases
Published 4/23/2018 in Lori Fenton's Blog Author lfenton
The wind on Mars is an artist, or at least it tries really hard to be one. It flutters up and down mountains, winding along valleys, dragging its wings in the sand and building up really amazing structures that could win any sand sculpture award. Well okay maybe I'm a little biased. Like this 0.92x1.325 km (0.57x0.82 mi) view (click to see the detail, it's worth it): HiRISE ESP_054171_1605, NASA/JPL/Univ. of Arizona A while back (maybe a million years or so), the wind blew sediment from the lower right to upper left, leaving behind some long, thin ripple-like things we call TARs. It even managed to pile up some little ones on the hilltops, which is pretty wild. But the wind kept blowing, pushing the TARs downwind towards the left. At some point, the area ran out of new sand to pile up into new TARs (the loose stuff exited stage right),... read more ❯

An Update on the Potential Habitability of TRAPPIST-1. No Aliens yet, but We’ve Learned a lot.
Published 4/20/2018 in Franck Marchis Blog Author Franck Marchis
One year ago, I wrote an article about the remarkable discovery of the TRAPPIST-1 planetary system, a system of seven temperate terrestrial planets orbiting an ultra-cool red dwarf star. This was an enormous astronomical discovery because these low-mass stars are the most numerous ones in our galaxy, and the discovery of potentially habitable planets around one of them led many people to speculate about the existence of life there and elsewhere in our galaxy around similar stars. This announcement also inspired a lot of additional studies by astronomers worldwide, who have used additional instruments and run complex models to better understand this planetary system and its potential for hosting life. One year later, it seems to me that the time is right to give you an update on what we’ve learned about this planetary system, which is located only 41 light-years from Earth. Better Understanding of the Planetary System Between December 2016 and March... read more ❯

Squish! ????
Published 4/20/2018 in Lori Fenton's Blog Author lfenton
This isn't a full blog post. Just something I saw while looking around for other things on Mars. And for once it's (probably) not related to the wind. But it's cool enough to share. I saw something that went "squish" ???? . This is a ~1.2 km (0.75 mi) wide crater in the northern mid-latitudes of Mars. I don't know much about this region geologically (haven't done my homework, as this is just a quick look). This crater has a set of layers in it that have partially eroded away. And underneath those layers on the crater floor are what look like the remnants of something that got 'sploded from underneath those layers. Judging from the direction of the 'sploded rays, it came from under that beak-shaped part of the layers. And I can sort of convince myself that maybe the squishing event happened once the layers got to the shape they're in now... read more ❯

Flow. Lots of flow.
Published 4/16/2018 in Lori Fenton's Blog Author lfenton
Over the years, many things have flowed across the surface of Mars: lava, ice, water, and wind. Two things have flowed in this image (the view is 0.75x0.6 km or 0.47x0.37 mi): Image credit: HiRISE ESP_026541_1840, NASA/JPL/Univ. of Arizona If you know my blog at all, then you might recognize the big structures as yardangs. They are part of an enormous set of yardangs on Mars called the Medusa Fossae Formation. At some point in the past, probably a few billion years ago, the wind kicked up a bunch of sand that carved out these structures, blowing from the lower left to the upper right. That's cool. But the thing to notice is the stuff around the yardangs. As the wind carved them out, it also created ripples. It's fairly normal to find ripples, especially coarse-grained ripples, in the troughs between yardangs, because a wind strong enough to carve out bedrock is also strong... read more ❯

My 2018 paper on recent climate change in Meridiani Planum, Mars (Part 3)
Published 4/13/2018 in Lori Fenton's Blog Author lfenton
This is the 3rd (and final) entry in a blog series describing a paper I recently published with colleagues in JGR Planets. Here are links to the previous two entries: Part 1, Part 2. Wow, I didn't think this would take 3 entries. Science is weird. You start a project feeling out of your depth, not knowing exactly where it will take you. You stumble around, read a bunch of papers to absorb the wisdom of others, and work up the courage to do things. You struggle mightily in doing those things: making the model run, keeping access to the computer system, making sure the model output is what you think it is, figuring out what you need to calculate and the best way of doing so. And then a bunch of refining and reworking and throwing out old ideas and trying new things, sometimes based on precious conversations with colleagues... read more ❯

My 2018 Paper on Recent Climate Change in Meridiani Planum, Mars (Part 2)
Published 4/12/2018 in Lori Fenton's Blog Author lfenton
In a previous post, I set the stage for my recently published paper in JGR Planets. A recap: we've got good evidence for a change in Mars's climate. Widespread ripples in Meridiani Planum formed >200,000 years ago, last migrated westward more than ~50,000 years ago, had their crests reformed into little dunes by a slightly different wind sometime after that, but have been dormant ever since. Meanwhile, we know that over that same time period, Mars' orbit and axial tilt have varied, which can affect wind patterns. Moreover, over this period, those same planetary changes led to a stepwise sequestration of atmospheric CO2 into the south polar ice cap, so that we know the air pressure was once higher than it is today. This too can affect wind patterns. All of these parameters can be plugged into a Mars global climate model (MGCM) to see if the model thinks the wind directions... read more ❯

My 2018 paper on recent climate change in Meridiani Planum, Mars (Part 1)
Published 4/11/2018 in Lori Fenton's Blog Author lfenton
Today a big thing happened: a paper I've spent a year or so working on has finally been published in the Journal of Geophysical Research: Planets (which we just call "JGR Planets"). Scientists write a lot of papers, so it's not as momentous as, say, graduating (or watching a student graduate), but it's still a really nice feeling. I can now download a PDF of the paper, look at all the pretty formatting, lovely figures and tables, pages of analysis and what I hope will turn out to be insightful discussion, and say "Yeah, I did that, and with some great colleagues. It's awesome". I'm going to try to explain what we did. If you can access the paper itself, you'll see that JGR now includes a "Plain Language Summary", the journal's attempt to reach a wider audience. It's not a bad idea in this era of ever-deepening specialization, so that... read more ❯

Wind-exposed layers
Published 3/26/2018 in Lori Fenton's Blog Author lfenton
On Earth, layers comprising the geological record of an area are most often exposed by fluvial erosion, as a river cuts through rock (a typical example is the Grand Canyon). On Mars, fluvial channels are not so common (especially in the past few billion years). But the wind has relentlessly worked away at the surface, sometimes revealing strata laid down long ago. Click on the image for more detail. This is a tiny bit (0.5x0.375 km, or 0.31x0.23 mi) of the side of an "Interior Layered Deposit" in the middle of Candor Chasma, called Juventae Mensa. Wind blowing from the upper left and upper right has eroded the whole area, eroding and exposing a bunch of layers. For some reason a bit of those layers is a little more resistant to erosion, where the wind has left behind a tiered hill (technically it's a sort of yardang). Each step on the... read more ❯