"Given enough time, the Earth will slow and the Moon will move further away. Both the day and the month will get longer until they match at about 40 "days" (I forget the exact value, and that's in terms of today's "day", of course)

But, you also have solar tides which act to brake the Earth's spin so once the Moon is tide-locked to the earth, it will commence a slow death spiral as the Earth slows. "Furtunately" this will take many tens of billions of years and the Sun will explode* first.

* No it won't really explode - it will merely turn into a red giant and bake the earth to a crisp, then subside to a white dwarf and the Earth will freeze - or it would if it had any atmosphere or oceans left, but they will be safely boiled off so instead it will be cold and dry...

...forever**"

Interesting how *most of us know this from Physics/Astronomy classes, yet, we're so comfortable and cozy in the here and now... and in general, oblivious.*

Our sense of wonder needs to go beyond Sci-fi (no, there's nothing wrong with sci-fi, but, it's not everything :)

P.S.: I'm glad the MER's are still in operation!!!

Steven W. Squyres & Andrew H. Knoll "Sedimentary rocks at Meridiani Planum: Origin, diagenesis, and implications for life on Mars". Earth and Planetary Science Letters 240 (2005) 1-10.

Abstract: The MER rover Opportunity has carried out the first outcrop-scale investigation of ancient sedimentary rocks on Mars. The rocks, exposed in craters and along fissures in Meridiani Planum, are sandstones formed via the erosion and re-deposition of fine grained siliciclastics and evaporates derived from the chemical weathering of olivine basalts by acidic waters. A stratigraphic section more than seven meters thick measured in Endurance crater is dominated by eolian dune and sand sheet facies; the uppermost half meter, however, exhibits festoon cross lamination at a length scale that indicates subaqueous deposition, likely in a playa-like interdune setting. Silicates and sulfate minerals dominate outcrop geochemistry, but hematite and Fe3D3 (another ferric iron phase) make up as much as 11% of the rocks by weight. Jarosite in the outcrop matrix indicates precipitation at low pH. Cements, hematitic concretions, and crystal molds attest to a complex history of early diagenesis, mediated by ambient ground waters. The depositional and early diagenetic paleoenvironment at Meridiani was arid, acidic, and oxidizing, a characterization that places strong constraints on astrobiologial inference.

** Sorry, Nick, but outside of my world, this has been a grand year for science and tech. Best to you and all here. Set your clocks accordingly.