In all the Phoenix flurry of news, let's not forget that the MER program is still going strong. Granted, it has been winter where they are, so one might expect both Spirit and Opportunity to be in hibernation mode to conserve energy until the Sun gets back to higher altitudes.

Having been working on Mars for about 1600 sols (martian days), the rovers have far outlived any expectations and continue to do significant work.

Spirit has been in a power-saving mode for some time now due to the fewer number of daylight hours, coupled with residual dust on the solar panels and in the air. During this time is has basically been "beeping" to let folks know its still operating; it has also been measuring the dust optical depth with its panorama cameras every few days. But now that the winter solstice has passed, things will be brightening up soon.

Opportunity has continued its journey down into Victoria Crater. It has been parked taking a full resolution panorama of the nearby Cape Verde layered cliff and a nearby region to give the images a larger context. There's no link to this yet as it's going to take weeks to get all the image sections beamed back to Earth.

You can see travel maps for both the rovers—the distances covered are incredible! Spirit has covered a total of 7,528.0 meters or 4.7 miles (as of 1 July 2008) and Opportunity has covered 11,723.94 meters or 7.28 miles (as of 4 July 2008). Impressive!

The mystery of "white stuff" composition is pretty much solved. After the first scooping, an image of the area showed a white substance within the trenches that could have been either salts or ices. However, comparison images taken 4 sols (martian days) later, showed that some of the white material has disappeared. The prevailing thought is that it must have been ice that sublimed away. You can read the full press release for more details.

Of course, Jon Stewert of The Daily Show, in his report on this event, has an entirely different interpretation. Warning, the clip from that link is rated PG. I guess we know that the Phoenix mission has "made it" in popular culture when it's getting spoofed on The Daily Show.

In other news, data and images from the CRISM instrument aboard the Mars Reconnaissance Orbiter has found evidence for gypsum and other sulfates north of the Phoenix landing site.

Gypsum is a water-bearing calcium sulfate mineral that is found on Earth in various sedimentary deposits. That is, it forms out of salty waters. Clearly, this has some implications on the past environment of the region that are very intriguing.

Things are going well with Phoenix these days. After a minor false start, there is now some martian "soil" in the Thermal and Evolved-Gas Analyzer (TEGA) oven. On the first attempt, none of the material passed through the millimeter-sized screening. This implies that the ground sort of clods together—which itself may be an interesting observation since it seems to be different from the material at other landing sites.

But persistence paid off and with some jiggling of the screen, and perhaps some changes to the clump over time as it sat there for a few days finally allowed material to fall in and fill the oven.

In orbiter Mars Reconnaissance Orbiter released an interesting image that shows one of the powers of using the infrared. In this image of the winter pole shows that in the IR the two types of ice (H₂O and CO₂) are distinguishable even though both appear white in visible light.

The reason for this is due to the chemical and structural differences in the two ices. The molecular bonds can be thought of as short springs that vibrate only at specific frequencies and energies. Infrared light has the amount of energy needed to excite these vibrations, but only very specific wavelengths in the infrared. Since the "springs" in the two ices are different, the specific infrared light absorbed to start the vibrations is different. So one type of ice will look dark at one wavelength (absorbing) while the other looks bright (not absorbing, so reflecting); the situation reverses at other wavelengths. This is the science of spectroscopy!

It's down, safe and sound! The first radio signals were received 7:53:44 p.m. Eastern Time confirming that the lander had touched down about 15 minutes earlier. If you go to the main Mars Phoenix site you'll see a picture of the landing pad on the ground—one of the first images transmitted back.

Since then, the solar panels and instruments have deployed and there's been a trickle of images coming back and posted to the site's Phoenix Screen Saver. I just tried it and there are even a couple color images!

After launching at about 4:45 am on 4 August 2007, traveling for months, the Mars Phoenix is set to land this coming Sunday 25 May 2008—and I can't wait to see the first images!

If you want a sneak peek of the "seven minutes of terror", known officially as EDL (entry, descent, and landing), the Phoenix team has a really nice simulation video at their site's videos page.

From their site, the lander will have a mere seven minutes to execute a sequence of maneuvers that will slow the craft from its incoming speed of almost 13,000 mph to the 5 mph needed for a save touchdown.

That's right, touchdown. Unlike the last two rovers, this one is not going to inflate balloons all around it and bounce to a stop. Mainly because its just too big for that trick to work. The rovers come in at about 185 kg (about 400 lb) but Phoenix is a whopping 350 kg (about 770 lb) and from what I read, the Spirit and Opportunity were at about the upper limits for the "bounce landing" to be safe.

Mars Phoenix is the rebirth of two missions, the Mars Polar Lander (which crashed on Mars back on 3 December 1999) and the Mars Surveyor Lander '01 (a mission that was canceled as part of NASA restructuring of the Mars Exploration Mission).

Phoenix will be landing in the far northern latitudes where previous missions (e.g. Mars Odyssey) have determined the presence of large amounts of sub-surface ice. Phoenix has a robotic arm and digging scoop so it will be doing some close up studies of the martian "soil". Included on board is a sort of next-generation "search for life" experiment that was back in the mid 70's by the Viking landers.

All in all, this is going to be a very exciting mission!