One reason I wanted to run yesterday's article about the Opher et al. paper on the heliosphere, aside from its innate scientific interest (and it is a very solid, well crafted piece of work) is to illustrate how much we still have to learn about the balloon-like bubble carved out by the solar wind. The entire Solar System fits within it easily, but we observe only from inside and have little knowledge of its structure. None of the paper's authors would argue that we have the definitive answer on the shape of the heliosphere. That will take a good deal more data, as the paper notes: Future remote-sensing and in situ measurements will be able to test the reality of a rounder heliosphere. In Fig. 6, we show our prediction for the interstellar magnetic field ahead of the heliosphere at V2. In addition, future missions such as the Interstellar Mapping and Acceleration Probe will return ENA [energetic neutral atom] maps at higher energies than present missions and so will be able to...

We have all too little information about the heliosphere, the only data from beyond it being what we have collected from the two Voyagers. Altogether, only five spacecraft -- Pioneer 10 and 11, the Voyagers and New Horizons -- have escaped the gravity of the Sun enroute to interstellar space. To understand how the heliosphere operates, and the interactions between the solar wind of charged particles and magnetic fields with what lies beyond, we’d really like to be able to look back at our system in its entirety. The Interstellar Probe concept being pondered at Johns Hopkins Applied Physics Laboratory and elsewhere is one possible way to do this. I’ll have more to say about Interstellar Probe in coming days, though I do want to give a nod to its history, which can be traced as far back as 1958 and a report from the National Academy of Sciences. APL’s Ralph McNutt has been studying interstellar concepts for decades, and was a major source as I worked on my original Centauri Dreams...

Centauri Dreams rarely looks at Mercury, the operative method being generally to focus on the outer Solar System and beyond. But a new paper out of the Planetary Science Institute in Tucson (AZ) raises the eyebrows in suggesting that parts of Mercury may once have been able to shelter prebiotic chemistry and perhaps, according to the authors, even primitive life forms. Such a finding might thus extend our ideas of ‘habitable zones’ much closer to parent stars than previously assumed. It seems a long shot, given surface temperatures reaching 430? in the daytime and -180? at night, but the PSI work turns up interesting possibilities in some subsurface regions of Mercury. The heart of this research is found in the datasets returned by the MESSENGER (MErcury Surface Space ENvironment GEochemistry and Ranging) spacecraft. The Mercury orbiter identified numerous volatile-bearing surfaces on Mercury, with high abundances of sulfur, chlorine and potassium, and polar ice in permanently...

With the James Webb Space Telescope now declared 'a fully assembled observatory' by NASA, environmental tests loom for the instrument, which is now slated for launch in March of 2021. Within that context, we need to place WFIRST (Wide-Field Infrared Space Telescope), whose development was delayed for several years because of cost overruns on JWST. Recall that WFIRST was the top priority for a flagship mission in the last astrophysics Decadal Survey. The good news is that NASA has just announced that WFIRST has passed what it is calling 'a critical programmatic and technical milestone,' which opens the path to hardware development and testing. With a viewing area 100 times larger than the Hubble instrument, WFIRST will be able to investigate dark energy and dark matter while at the same time examining exoplanets by using microlensing techniques applied to the inner Milky Way. Its exoplanet capabilities could be significantly extended if additional budgeting for a coronagraph -- which...

The fault protection routines programmed into Voyager 1 and 2 were designed to protect the spacecraft in the event of unforeseen circumstances. Such an event occurred in late January, when a rotation maneuver planned to calibrate Voyager 2's onboard magnetic field instrument failed to occur because an unexpected delay in its execution left two systems consuming high levels of power (in Voyager terms) at the same time, overdrawing the available power supply. We looked at this event not long after it happened, and noted that within a couple of days, the Voyager team was able to turn off one of the systems and turn the science instruments back on. Normal operations aboard Voyager 2 were announced on March 3, with five operating science instruments that had been turned off once again returning their data. Such autonomous operation is reassuring because Voyager 2 is now going to lose the ability to receive commands from Earth, owing to upgrades to the Deep Space Network in Australia. This...

Centauri Dreams reader Charley Howard recently wrote to ask about how NASA goes about setting its mission priorities and analyzing mission concepts like potential orbiter missions to the ice giants. It's such a good question that I floated it past Ashley Baldwin, who is immersed in the evolution of deep space missions and moves easily within the NASA structure to extract relevant information. Dr. Baldwin had recently commented on ice giant mission analysis by the Outer Planets Advisory Group. But what is this group, and where does it fit within the NASA hierarchy? Here is Ashley's explanation of this along with links to excellent sources of information on the various mission concepts under analysis for various targets, and a bit of trenchant commentary. By Ashley Baldwin Each of the relevant NASA advisory groups has its own page on the NASA site with archives stuffed full of great presentations. The most germane to our discussion here is the Outer Planets Assessment Group (OPAG). My...