Starter? or solenoid or fuse?
 

This is the wife's car that she doesn't drive much any more but i will use about once a week if she doesn't.
2001 MGM 4.6L 160K miles.

She left this morning to go meet friends for a movie. Got to friends house, came back out won't start again.
They took friends car and I ran over to investigate. All other electrical is working; interior lights, radio, heater, etc.
New (1yo) battery. New alternator, less than 1yo. Tried jumping. Do not even get a click from starter.
Is it possible, the starter failed without warning? Or is there a fuse or solenoid I should look at before replacing the starter?

Two things I would look into. First try tapping the starter with a hammer and see if it cranks. If it does, replace the starter. Second, I do recall a TSB regarding a problem like this. I know it applied to 2003's and may possibly your 2001. Look at the cable which attaches at the starter. It seems it gets strained and it not fastened properly and the connection snaps off the starter. Worth a look.
Lastly, hang a volt meter at the starter and have a helper try starting and see if you have 12v present.

Had the exact same problem -- after making sure there was 12 volts to the Starter. Still no crank.
The OEM starter is a gear-reduction type -- that should NEVER be hit with a hammer or bashed with a rock.
That old "trick" was from back in the days of cheap, 2-pole starters from Chevy.
Ford always used a better-made starter, and Fords were famous for starting in the Arctic cold.
Like yours, mine had 160,000 miles on the clock. Time for some serious preventative maintenance !!
Installed NEW (NOT rebuilt!) Bosch #SR7533N Starter -- MUCH better quality than the original.
EXCELLENT prices from Amazon.com. or RockAuto.com.
95 MERC starts INSTANTLY -- better than ever !!

Tapping the starter is not the same as hitting or bashing and has nothing to do with Chevy. The old trick works with any starter, I have done it and has gotten me out of a bad situations before..
I will let everyone know in Canada that they need to buy a Ford because they are famous for starting in the Arctic cold ..LOL....
You claimed Fords have the best starters, which his is 18 years old and has 160k (and yours) why would he not go with OEM and go with a Bosch? You don't make sense and make these claims all the time with no facts to back them up and just your opinion. Just a lot of double talk.
The OEM starter has already proven itself with its longevity.

OK, so you're gonna defend the tapping, hitting, striking, whatever -- of a starter -- because you've done it before.
And you're bad-mouthing me because I say NOT to do that -- BUT --
It's mighty funny that there are NO Factory Shop Manuals that advise such a practice -- AND -- the new Bosch starter even has a WARNING LABEL on the starter that says: DO NOT STRIKE WITH HAMMER!
You seem to have great difficulty in comprehending words as they are written, or perhaps you just have a know-it-all attitude. I don't know, it's just what I see coming from your overly-aggressive, trollish remarks.
You see, I did not "claim that Ford has the best starters". I just said that the Ford 3-pole starter is superior to the Chevy 2-pole starter, especially in the colder climates.
While serving in Alaska, I was assigned to the Motor Pool, where it soon became evident that the Fords would start when the Chevys and Dodges wouldn't. Being originally from PA, I had no clue -- but the old-timers there set me straight. Fords started when others didn't.
Your condescending remarks do not change that fact.
Yes, that fellow's OEM starter lasted him 18 years -- and mine lasted for 24 years -- roughly the same miles on both cars. Most people would replace it with a Re-manufactured unit, but I wanted to replace mine with the best-made starter that I could find, regardless of price.
My search lead me to the Bosch #SR7533N, and upon close examination of the unit, it's workmanship, and it's specs, I went with the Bosch unit. The difference in workmanship and materials is immediately evident, and a good price was available from both Amazon.com and RockAuto.com.
The last part of your post is pretty much a personal attack, so it has no meaning or purpose to inform other forum participants, and thus, rates no response.

I am not personally attacking you but your advice is often skewed. You are always saying this is best (always Bosch) and offer NO FACTS ever. Until you post pictures of both starters disassembled and show the differences, your opinions are just that. Why not post pictures and the specs you state you have seen on both starters and you might convince me.
Tapping on a starter is a gentle tap and I never mentioned primitive methods such as rock bashing the starter as you mentioned. You must not understand that. If that can damage a Bosch starter, I would not want to install one on my vehicle because what that starter is likely to face hanging under the car is far more abusive than that.Also, if someone is stranded somewhere, who are you to say not to tap on the starter because you feel it is wrong if it can possibly get the car going so they can drive it home?
Finally, just because tapping on a starter is not listed in a service manual does not mean you cannot do it with positive results.Example, I never seen anywhere published in a manual not to prefill your oil filter before installing it but people do it to get oil pumping quicker after an oil change.
You need to get off your soap box and stop acting like a Bosch sales rep and answer the poster's question and stop pushing your favorite brand products because you "think" they are best for a Mercury G.M. as I have seen from your past episodes.
Have a nice day!